Method for producing glass fiber reinforced composites

Abstract

The present invention relates to a method for producing a glass fiber reinforced thermoplastic polymer composition, the method comprising the following sequential steps: a) unwinding at least one first continuous glass multifilament strand having a first filament thickness t1 from a first package and unwinding at least one second continuous glass multifilament strand having a second filament thickness t2 greater than the first filament thickness t1 from a second package, and b) applying a sheath of a thermoplastic polymer composition around the at least one first continuous glass multifilament strand and the at least one second continuous glass multifilament strand to form a sheathed continuous multifilament strand comprising the at least one first continuous glass multifilament strand and the at least one second continuous glass multifilament strand.

Description

[0001] The present invention relates to a method for producing a glass fiber reinforced thermoplastic polymer composition, the method comprising the steps of unwinding a continuous glass multifilament strand from a package and applying a sheath of polypropylene around the multifilament strand to form a sheathed continuous multifilament strand.

[0002] Such a method is known from the international application WO 2009 / 080281. This published patent application discloses a method for producing a long glass fiber reinforced thermoplastic polymer composition, the method comprising the steps of: i) unwinding at least one continuous glass multifilament strand from a package, ii) applying an impregnating agent to the at least one continuous glass multifilament strand to form an impregnated continuous multifilament strand, and iii) applying a sheath of a thermoplastic polymer around the impregnated continuous multifilament strand to form a sheathed continuous multifilament strand. WO 2009 / 080281 does not disclose applying one sheath around more than one glass multifilament strand.

[0003] US2016279833 discloses applying a sheath around at least two glass multi-filament strands.

[0004] A variety of properties are important for such compositions. For example, a certain amount of glass fibers mechanically break away from the long glass fiber reinforced composition, which is the so-called free glass. It is desirable that the amount of this free glass is less. In addition, it is desirable that the distribution of glass fibers in the molded article made from the composition is uniform. In addition, the mechanical properties of the composition such as impact strength and tensile properties are important.

[0005] An object of the present invention is to provide a long glass fiber reinforced thermoplastic polymer composition having balanced properties with respect to free glass, glass fiber distribution and mechanical properties.

[0006] Therefore, the present invention provides a method for producing a glass fiber reinforced thermoplastic polymer composition, the method comprising the following sequential steps:

[0007] a) unwinding at least one first continuous glass multifilament strand having a first filament thickness t1 from a first package and unwinding at least one second continuous glass multifilament strand having a second filament thickness t2 greater than the first filament thickness t1 from a second package, and

[0008] b) applying a sheath of a thermoplastic polymer composition around the at least one first continuous glass multifilament strand and the at least one second continuous glass multifilament strand to form a sheathed continuous multifilament strand comprising the at least one first continuous glass multifilament strand and the at least one second continuous glass multifilament strand.

[0009] Surprisingly, the inventors have found that by using strands with a small thickness the amount of free glass is reduced and thus the problem of free glass can be solved by the choice of thickness. Small thickness also gives better results in terms of tensile properties. However, it has also been observed that using strands with a small thickness produces worse results in terms of glass fiber distribution. Thus, the inventors have realized that using strands with two different thicknesses provides a composition with balanced properties with respect to free glass, glass fiber distribution and mechanical properties.

[0010] Step a)

[0011] Continuous glass multifilament strand

[0012] Glass fibers are generally supplied as multiple continuous, very long filaments, and in the form of strands, rovings, or yarns. A filament is a single fiber of a reinforcing material. A strand is a plurality of bundled filaments. A yarn is a collection of strands, such as strands twisted together. A roving refers to a collection of strands wound into a package. Glass multifilament strands and their preparation are known in the art.

[0013] For purposes of the present invention, a glass multifilament strand is defined as a plurality of bundled glass filaments.

[0014] The thickness of the filaments in the continuous glass multifilament strand is substantially the same, but it will be understood that there may be minor variations. Thus, a first continuous glass multifilament strand having a first filament thickness t1 means that the strand is composed of filaments each having a thickness substantially equal to t1. The term "substantially equal to t1" may mean that the difference between the thickness of the filaments and t1 is at most 15% of t1. Similarly, a second continuous glass multifilament strand having a second filament thickness t2 means that the strand is composed of filaments each having a thickness substantially equal to t2. The term "substantially equal to t2" may mean that the difference between the thickness of the filaments and t2 is at most 15% of t2.

[0015] According to the invention, at least a first strand with a filament thickness t1 and a second strand with a filament thickness t2 are used. The filament thickness t2 is greater than t1. Preferably, t2 is at least 1 μm greater than t1, for example 1 to 30 μm or 5 to 20 μm greater than t1.

[0016] Preferably, t1 is 1 to 45 μm, for example 2 to 40 μm, 3 to 30 μm, 5 to 20 μm or 10 to 15 μm.

[0017] Preferably, t2 is 3 to 50 μm, for example, 5 to 45 μm, 10 to 40 μm, 15 to 35 μm or 20 to 30 μm.

[0018] In a particularly preferred embodiment, t1 is from 10 to 15 μm and t2 is from 20 to 30 μm.

[0019] Typically the cross section of the glass filaments in a multifilament strand is circular, meaning that the thickness as defined above will refer to the diameter. For example, where the cross section of the glass filaments in a multifilament strand is polygonal, meaning that the thickness as defined above will be 2d, where d is the distance between the geometric center of the polygon and the side closest to the geometric center.

[0020] The strand density of the continuous glass multifilament strand can vary within wide limits. For example, the continuous glass multifilament strand can have at least 500, such as at least 1000 glass filaments per strand and / or at most 10000, such as at most 5000 grams per 1000 meters. Preferably, the amount of each glass filament is 500 to 10000 grams per 1000 meters of glass filament.

[0021] The length of the glass filament strand is in principle not limited, since it is substantially equal to the length of the sheathed continuous multifilament strand. However, for practical reasons of being able to handle the sheathed continuous multifilament strand, it may be necessary to cut the sheathed continuous multifilament strand into shorter strands. For example, the length of the sheathed continuous multifilament strand is at least 1 m, such as at least 10 m, such as at least 50 m, such as at least 100 m, such as at least 250 m, such as at least 500 m and / or such as at most 25 km, such as at most 10 km.

[0022] Preferably, in the composition of the present invention, the continuous glass multifilament strand comprises up to 2 wt%, preferably 0.10 to 1 wt% sizing agent based on the continuous glass multifilament strand. The amount of sizing agent can be determined using ISO 1887:2014.

[0023] The sizing composition is typically applied to the glass filaments before the glass filaments are bundled into a continuous glass multi-filament strand.

[0024] Suitable examples of sizing compositions include solvent based compositions, such as organic materials dissolved in aqueous solutions or dispersed in water and melt based or radiation curable compositions.Preferably, the sizing composition is an aqueous sizing composition.

[0025] The aqueous sizing composition may comprise a film former, a coupling agent and other additional components as described in the art, for example in documents EP1460166A1, EP0206189A1 or US4338233.

[0026] The film former is generally present in an effective amount to protect the fiber from interfilament abrasion and provide integrity and processability of the fiber strand after drying. Suitable film formers are miscible with the polymer to be reinforced. For example, for reinforced polypropylene, suitable film formers generally include polyolefin waxes.

[0027] Coupling agent is generally used to improve the adhesion between the matrix thermoplastic polymer and the fiber reinforcement. Suitable examples of coupling agents known in the art for glass fiber include organofunctional silanes. More specifically, the coupling agent added to the sizing composition is aminosilane, such as aminomethyl-trimethoxysilane, N-(β-aminoethyl)-γ-aminopropyl-trimethoxysilane, γ-aminopropyl-trimethoxysilane, γ-methylaminopropyl-trimethoxysilane, δ-aminobutyl-triethoxysilane, 1,4-aminophenyl-trimethoxysilane. Preferably, in the tape of the present invention, the sizing composition contains aminosilane to achieve good adhesion to the thermoplastic matrix. The sizing composition may also include any other components known to those skilled in the art to be suitable for the sizing composition. Suitable examples include but are not limited to lubricants (used to prevent damage to strands due to wear), antistatic agents, crosslinking agents, plasticizers, surfactants, nucleating agents, antioxidants, pigments and mixtures thereof.

[0028] Typically, after the sizing composition is applied to the glass filaments, the filaments are bundled into a continuous glass multi-filament strand and then wound onto a spool to form a package.

[0029] Step a1)

[0030] Impregnation agent

[0031] Preferably, the method further comprises a step a1) between steps a) and b). Step a1) is a step of applying an impregnating agent to each of the continuous glass multifilament strands to be sheathed in step b).

[0032] The impregnant may be applied to each of the continuous glass multi-filament strands together or separately.

[0033] The optimum amount of the impregnating agent applied to continuous glass multifilament strand depends on polymer sheath, forms the thickness (diameter) of the glass filaments of continuous glass strand, and the type of sizing composition.Usually, the amount of the impregnating agent applied to continuous glass multifilament strand is based on the amount of sheathed continuous multifilament strand at least 0.50 weight %, preferably at least 1.0 weight %, preferably at least 1.5 weight %, preferably at least 2 weight %, preferably at least 2.5 weight % and / or at most 18.0 weight %, preferably at most 15.0 weight %, for example at most 10.0 weight %, at most 9.0 weight %, at most 8.0 weight %, at most 7.0 weight %, at most 6.0 weight %, at most 5.5 weight %.A larger amount of impregnating agent improves per unit thickness impact energy (J / mm).However, for cost-effectiveness and low emission (volatile organic compound) and mechanical property, the amount of impregnating agent should not become too high either.

[0034] For example, the ratio of impregnating agent to continuous glass multifilament strand is from 1:4 to 1:30, preferably from 1:5 to 1:20.

[0035] Preferably, the viscosity of the impregnating agent is from 2.5 to 200 cSt at 160°C, more preferably at least 5.0 cSt, more preferably at least 7.0 cSt and / or at most 150.0 cSt at 160°C, preferably at most 125.0 cSt, preferably at most 100.0 cSt.

[0036] Impregnating agents with too high a viscosity are difficult to apply to continuous glass multifilament strands. Low viscosity is required to promote good wetting properties of the fibers, but impregnating agents with viscosities below 2.5 cSt are difficult to handle, e.g., it is difficult to control the amount to be applied; and the impregnating agent may become volatile. For purposes of the present invention, unless otherwise specified, the viscosity of the impregnating agent is measured at 160°C according to ASTM D3236-15 (Standard Test Method for Apparent Viscosity of Hot Melt Adhesives and Coatings).

[0037] Preferably, the melting point (the lowest melting temperature in the melting temperature range) of the impregnating agent is at least 20° C. lower than the melting point of the thermoplastic polymer composition. More preferably, the impregnating agent has a melting point at least 25 or 30° C. lower than the melting point of the thermoplastic polymer composition. For example, when the thermoplastic polymer composition has a melting point of about 160° C., the melting point of the impregnating agent may be up to about 140° C.

[0038] Suitable impregnating agents are compatible with the thermoplastic polymer to be reinforced and possibly even soluble in said polymer.The skilled person can select suitable combinations based on general knowledge and can also find such combinations in the art.

[0039] Suitable examples of impregnants include low molar mass compounds, for example low molar mass or oligomeric polyurethanes, polyesters such as unsaturated polyesters, polycaprolactones, polyethylene terephthalate, polyalphaolefins such as highly branched polyethylene and polypropylene, polyamides such as nylon, and other hydrocarbon resins.

[0040] For reinforced polypropylene, the impregnating agent preferably comprises a highly branched poly-alpha-olefin, such as highly branched polyethylene, a modified low molecular weight polypropylene, a mineral oil, such as paraffin or silicon and any mixtures of these compounds.

[0041] The impregnating agent preferably comprises at least 20 wt%, more preferably at least 30 wt%, more preferably at least 50 wt%, such as at least 99.5 wt%, such as 100 wt% of a branched polyalphaolefin, most preferably a branched polyethylene.

[0042] In order to make the impregnant reach a viscosity of 2.5 to 200 cSt at 160°C, the branched polyalphaolefin may be mixed with an oil selected from the group consisting of: mineral oil, such as paraffin oil or silicone oil; hydrocarbon oil; and any mixture thereof.

[0043] Preferably, the impregnating agent is non-volatile, and / or substantially solvent-free. In the context of the present invention, "non-volatile" means that the impregnating agent has a boiling point or boiling range above the temperature at which the impregnating agent is applied to the continuous multi-filament glass strand. In the context of the present invention, "substantially solvent-free" means that the impregnating agent contains less than 10% by weight of solvent, preferably less than 5% by weight of solvent, based on the impregnating agent. In a preferred embodiment, the impregnating agent does not contain any organic solvent.

[0044] The impregnating agent can be further mixed with other additives known in the art. Suitable examples include lubricants, antistatic agents, UV stabilizers, plasticizers, surfactants, nucleating agents, antioxidants, pigments, dyes, and adhesion promoters, such as modified polypropylene with maleated reactive groups, and any combination thereof, provided that the viscosity remains within the desired range. Any method known in the art can be used to apply the liquid impregnating agent to the continuous glass multifilament strand. The application of the liquid impregnating agent can be carried out using a mold. Other suitable methods for applying the impregnating agent to the continuous multifilament strand include an applicator, a roller and a hot melt applicator with a belt. Such methods are, for example, described in documents EP0921919B1, EP0994978B1, EP0397505B1, WO2014 / 053590A1 and the references cited therein. The method used should enable a constant amount of impregnating agent to be applied to the continuous multifilament strand.

[0045] Step b)

[0046] Polymer sheath

[0047] The polymer sheath is composed of a thermoplastic polymer composition.

[0048] Preferably, the thermoplastic polymer has a melt flow index (MFI) of at least 1 dg / min, such as 20 to 150 dg / min, preferably 25 to 120 dg / min, such as 35 to 100 dg / min, measured according to ISO 1133-1:2011 (2.16 kg / 230°C).

[0049] Thermoplastic Polymer The composition preferably comprises a thermoplastic polymer.

[0050] Suitable examples of thermoplastic polymers include, but are not limited to, polyamides such as polyamide 6, polyamide 66, or polyamide 46; polyolefins, for example polypropylene and polyethylene; polyesters such as polyethylene terephthalate, polybutylene terephthalate; polycarbonates; polyphenylene sulfide; polyurethanes, and mixtures thereof.

[0051] The thermoplastic polymer is preferably a polyolefin, more preferably a polyolefin selected from the group of polypropylene or an elastomer of ethylene and an alpha-olefin comonomer having 4 to 8 carbon atoms, and any mixture thereof.

[0052] In one embodiment, preferably the thermoplastic polymer composition comprises at least 80 wt% of a thermoplastic polymer, such as at least 90 wt% of a polyolefin, at least 93 wt%, such as at least 95 wt%, such as at least 97 wt% of a thermoplastic polymer, such as at least 98 wt% or such as at least 99 wt% of a thermoplastic polymer, based on the thermoplastic polymer composition. In a specific embodiment, the thermoplastic polymer composition consists of a thermoplastic polymer.

[0053] In another embodiment, the thermoplastic polymer composition comprises at least 60 wt%, such as at least 70 wt%, such as at least 75 wt% and / or up to 99 wt%, such as up to 95 wt%, such as up to 90 wt% thermoplastic polymer.

[0054] The polypropylene may be, for example, a propylene homopolymer or a random propylene-α-olefin copolymer or a heterophasic propylene copolymer.

[0055] Propylene homopolymers can be obtained by polymerizing propylene under suitable polymerization conditions. Propylene copolymers can be obtained by copolymerizing propylene and one or more other α-olefins, preferably ethylene, under suitable polymerization conditions. The preparation of propylene homopolymers and copolymers is described, for example, in Moore, EP (1996) Polypropylene Handbook. Polymerization, Characterization, Properties, Processing, Applications, Hanser Publishers: New York.

[0056] The α-olefin in the random propylene α-olefin copolymer is, for example, an α-olefin selected from the group of α-olefins having 2 or 4 to 10 C atoms, preferably ethylene, 1-butene, 1-hexene or any mixture thereof. The amount of the α-olefin is preferably up to 10 wt %, based on the propylene α-olefin copolymer, for example 2-7 wt %, based on the propylene α-olefin copolymer.

[0057] The polypropylene can be produced by any known polymerization technique and using any known polymerization catalyst system. As regards the techniques, mention may be made of slurry, solution or gas phase polymerization; as regards the catalyst systems, mention may be made of Ziegler-Natta, metallocene or single site catalyst systems. All are known per se in the art.

[0058] Heterophasic propylene copolymers are generally prepared in one or more reactors by polymerizing propylene in the presence of a catalyst and subsequently polymerizing a propylene-α-olefin mixture. The resulting polymeric material is heterophasic, but the specific morphology usually depends on the preparation method and the monomer ratio.

[0059] The heterophasic propylene copolymer as defined herein consists of a propylene based matrix and a dispersed ethylene-α-olefin copolymer.

[0060] The propylene based matrix typically forms the continuous phase in the heterophasic propylene copolymer.

[0061] The propylene-based matrix consists of a propylene homopolymer and / or a propylene copolymer consisting of at least 70 wt% of propylene monomer units and up to 30 wt% of comonomer units selected from ethylene monomer units and α-olefin monomer units having 4 to 10 carbon atoms, such as at least 80 wt% of propylene monomer units and up to 20 wt% of comonomer units, at least 90 wt% of propylene monomer units and up to 10 wt% of comonomer units, or at least 95 wt% of propylene monomer units and up to 5 wt% of comonomer units, based on the total weight of the propylene-based matrix.

[0062] Preferably, the comonomer in the propylene copolymer of the propylene based matrix is ​​selected from the group of ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene and 1-octene, and is preferably ethylene.

[0063] Preferably, the propylene based matrix consists of a propylene homopolymer.

[0064] The melt flow index (MFI) of the propylene-based matrix (before being mixed into the composition of the present invention) may be, for example, 0.3 to 200 dg / min, measured according to ISO 1133-1:2011 (2.16 kg / 230°C).

[0065] The propylene based matrix is ​​for example present in an amount of 50 to 85 wt.-%, based on the total heterophasic propylene copolymer.

[0066] Apart from the propylene based matrix the heterophasic propylene copolymer comprises dispersed ethylene-α-olefin copolymer. The dispersed ethylene-α-olefin copolymer is herein also referred to as 'dispersed phase'. The dispersed phase is embedded in the heterophasic propylene copolymer in discontinuous form.

[0067] The MFI of the dispersed ethylene α-olefin copolymer may vary between wide ranges and may be, for example, from 0.001 to 10 dg / min measured according to ISO 1133 (2.16 kg / 230° C.), as calculated using the following formula:

[0068]

[0069] wherein MFI Heterophasic is the melt flow index of the heterophasic propylene copolymer measured according to ISO 1133-1:2011 (2.16 kg / 230° C.),

[0070] MFI PP is the MFI of the propylene based matrix of the heterophasic propylene copolymer measured according to ISO 1133 (2.16 kg / 230°C),

[0071] The matrix content is the fraction of the propylene based matrix in the heterophasic propylene copolymer, and

[0072] Rubber content is the fraction of ethylene α-olefin copolymer in the heterophasic propylene copolymer. The sum of matrix content and rubber content is 1. For the avoidance of any doubt, Log in the formula means log 10 .

[0073] The dispersed ethylene-α-olefin copolymer is for example present in an amount of 50 to 15 wt.-%, based on the total heterophasic propylene copolymer.

[0074] For example, the amount of the ethylene monomer unit (RCC2) in the ethylene-α-olefin copolymer is 20 to 65 wt % based on the ethylene-α-olefin copolymer.

[0075] As is well known in the art, the amount of the propylene-based matrix and dispersed ethylene-α-olefin copolymers, and the amount of ethylene in the ethylene α-olefin copolymers, can be determined by 13 C-NMR determination.

[0076] In the heterophasic polypropylene the sum of the total weight of the propylene based matrix and the total weight of the dispersed ethylene-α-olefin copolymer is 100 wt%.

[0077] The α-olefin in the ethylene-α-olefin copolymer is preferably selected from the group of α-olefins having 3 to 8 carbon atoms and any mixture thereof, preferably the α-olefin in the ethylene-α-olefin copolymer is selected from the group of α-olefins having 3 to 4 carbon atoms and any mixture thereof, more preferably the α-olefin is propylene, in which case the ethylene-α-olefin copolymer is an ethylene-propylene copolymer. Examples of suitable α-olefins having 3 to 8 carbon atoms that can be employed as ethylene comonomers to form ethylene α-olefin copolymers include, but are not limited to, propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, and 1-octene.

[0078] Elastomers of ethylene and an α-olefin comonomer having 4 to 8 carbon atoms may, for example, have a molecular weight of 0.850 to 0.915 g / cm 3 This type of elastomer is sometimes called a plastomer.

[0079] The α-olefin comonomer in the elastomer is preferably an acyclic monoolefin such as 1-butene, 1-pentene, 1-hexene, 1-octene or 4-methylpentene.

[0080] Thus, the elastomer is preferably selected from the group consisting of ethylene-1-butene copolymers, ethylene-1-hexene copolymers, ethylene-1-octene copolymers and mixtures thereof, more preferably wherein the elastomer is selected from ethylene-1-octene copolymers. Most preferably, the elastomer is ethylene-1-octene copolymers.

[0081] Preferably, the density of the elastomer is at least 0.865 g / cm 3 and / or up to 0.910 g / cm 3 For example, the density of the elastomer is at least 0.850, such as at least 0.865, such as at least 0.88, such as at least 0.90 and / or such as at most 0.915, such as at most 0.910, such as at most 0.907, such as at most 0.906 g / cm 3 More preferably, the density of the elastomer is from 0.88 up to and including 0.907 g / cm 3 Most preferably, the density of the elastomer is from 0.90 to and including 0.906 g / cm 3 .

[0082] Elastomers suitable for use in the present invention are commercially available, for example, from Exxon Chemical Company of Houston, Texas under the trademark EXACT TM ENGAGE TMThe polymers are commercially available from MITSUI Chemicals Group of Tokyo, Minato, under the trademark TAFMER TM Nexlene TM Purchased.

[0083] Elastomers can be prepared using methods known in the art, such as by using a single-site catalyst, i.e., a catalyst in which the transition metal component is an organometallic compound and in which at least one ligand has a cyclopentadienyl anionic structure, which is bonded and coordinated to the transition metal cation through the anionic structure. This type of catalyst is also known as a "metallocene" catalyst. Metallocene catalysts are described, for example, in U.S. Patent Nos. 5,017,714 and 5,324,820. Elastomers can also be prepared using conventional types of heterogeneous multisite Ziegler-Natta catalysts.

[0084] Preferably, the elastomer has a melt flow index of 0.1 to 40 dg / min (ISO 1133, 2.16 kg, 190° C.), such as at least 1 dg / min and / or at most 35 dg / min. More preferably, the elastomer has a melt flow index of at least 1.5 dg / min, such as at least 2 dg / min, such as at least 2.5 dg / min, such as at least 3 dg / min, more preferably at least 5 dg / min and / or preferably at most 30 dg / min, more preferably at most 20 dg / min, more preferably at most 10 dg / min, measured according to ISO 1133 using a 2.16 kg weight and at a temperature of 190° C.

[0085] Preferably, the amount of ethylene incorporated into the elastomer is at least 50 mol%. More preferably, the amount of ethylene incorporated into the elastomer is at least 57 mol%, such as at least 60 mol%, at least 65 mol%, or at least 70 mol%. Even more preferably, the amount of ethylene incorporated into the elastomer is at least 75 mol%. The amount of ethylene incorporated into the elastomer can generally be up to 97.5 mol%, such as up to 95 mol% or up to 90 mol%.

[0086] Thermoplastic polymer compositions can contain conventional additives, such as nucleating agents and clarifying agents, stabilizers, release agents, fillers, peroxides, plasticizers, antioxidants, lubricants, antistatic agents, crosslinking agents, anti-scratch agents, high-performance fillers, pigments and / or colorants, impact modifiers, flame retardants, foaming agents, acid scavengers, circulation additives, coupling agents, antimicrobial agents, antifogging additives, slip additives, anti-blocking additives, polymer processing aids and the like. Such additives are well known in the art. Another example of additive is a coupling agent, which may or may not belong to the same type as the coupling agent that may be present in the aqueous sizing composition. The technician will understand how to select the type and amount of additives so that they do not adversely affect the target properties. In a specific embodiment, the thermoplastic polymer composition is composed of a thermoplastic polymer and an additive.

[0087] Preferably, the amount of glass is 10 to 70 wt%, such as 15 to 65 wt%, such as 20 to 60 wt% or such as 25 to 55 wt%, based on the sheathed continuous multifilament strand.

[0088] Preferably, the amount of the impregnated continuous multifilament strand is 10 to 70 wt %, such as 15 to 65 wt %, such as 20 to 60 wt % or such as 25 to 55 wt % based on the sheathed continuous multifilament strand. Preferably, the sum of the amount of the impregnated continuous multifilament strand and the polymer sheath is 100 wt %.

[0089] The method according to the present invention may comprise using, in addition to the first and second continuous glass multifilaments, one or more continuous glass multifilament strands having a filament thickness different from the filament thickness of the first and second continuous glass multifilaments.

[0090] Thus, in some embodiments,

[0091] Step a) comprises unwinding from a third package at least one third continuous glass multifilament strand having a third filament thickness t3, wherein t3 is different from t1 and t2, and

[0092] Step b) includes applying a sheath around at least one third continuous glass multifilament, and the sheathed continuous multifilament strand further comprises at least one third continuous glass multifilament.

[0093] Preferably, the method further comprises the step of cutting the sheathed continuous glass multifilament strand into pellets. Any suitable method known in the art, such as using the apparatus mentioned in document EP0994978B1, can be used in the present invention. The length of the glass fibers in the pellets or granules is generally about the same as the length of the pellets or granules, and can vary from 0.8 to 50 mm, preferably 2 to 50 mm, preferably 5 to 30 mm, more preferably 6 to 20 and most preferably 10 to 15 mm.

[0094] In another aspect, the present invention relates to a glass-fiber reinforced thermoplastic polymer composition obtainable or obtainable by the process according to the present invention.

[0095] In another aspect, the present invention provides a glass fiber reinforced thermoplastic polymer composition comprising a sheathed continuous multifilament strand, the sheathed continuous multifilament strand comprising at least one first glass multifilament strand having a first filament thickness t1 and at least one second continuous glass multifilament strand having a second filament thickness t2 greater than the first filament thickness t1, and a sheath of the thermoplastic polymer composition provided around at least one first continuous glass multifilament strand and at least one second continuous glass multifilament. This glass fiber reinforced thermoplastic polymer composition may also contain additional components described with respect to the method according to the present invention and the glass fiber reinforced thermoplastic polymer composition obtained by or by the method. Suitable examples of components present in this glass fiber reinforced thermoplastic polymer composition are those described with respect to the method according to the present invention and the glass fiber reinforced thermoplastic polymer composition obtained by or by the method. In particular, it is mentioned that the first glass multifilament strand and the second glass multifilament strand in the glass fiber reinforced thermoplastic polymer composition are preferably the same first glass multifilament strand and the same second glass multifilament strand as in the above-mentioned step a). Preferably, the glass fiber reinforced thermoplastic polymer composition further comprises an impregnating agent between the glass multifilament strands and the sheath of the thermoplastic polymer composition, wherein the impregnating agent is the same impregnating agent as in step a1) above. Preferably, the thermoplastic polymer composition in the glass fiber reinforced thermoplastic polymer composition is the same thermoplastic polymer composition as in step b) above. In another aspect, the present invention provides pellets consisting of such glass fiber reinforced thermoplastic polymer composition, wherein the length of the glass fibers in the pellets is generally about the same as the pellet length and can vary from 0.8 to 50 mm, preferably from 2 to 50 mm, preferably from 5 to 30 mm, more preferably from 6 to 20 and most preferably from 10 to 15 mm.

[0096] In another aspect, the present invention relates to molding a glass fiber reinforced thermoplastic polymer composition into an article.

[0097] In another aspect, the invention relates to an article comprising a composition according to the invention. The article can be used, for example, in automotive applications.

[0098] In another aspect, the invention relates to the use of a composition according to the invention for the manufacture of automotive articles.

[0099] It is noted that the present invention relates to all possible combinations of features described herein, preferably in particular those combinations of features presented in the claims. Thus, it is to be understood that all combinations of features relating to the composition according to the invention, all combinations of features relating to the method according to the invention, as well as all combinations of features relating to the composition according to the invention and all combinations of features relating to the method according to the invention are described herein.

[0100] It is further noted that the terms 'comprising', 'including' do not exclude the presence of other elements. However, it is also understood that the description of a product / composition comprising certain components also discloses a product / composition consisting of these components. A product / composition consisting of these components may be advantageous because it provides a simpler and more economical method for preparing the product / composition. Similarly, it is also understood that the description of a method comprising certain steps also discloses a method consisting of these steps. A method consisting of these steps may be advantageous because it provides a simpler and more economical method.

[0101] When a value is stated for a lower limit and an upper limit for a parameter, it is understood that a range combining the value of the lower limit and the value of the upper limit is also disclosed.

[0102] The present invention is now illustrated with the aid of the following examples, but the invention is not limited thereto. Example

[0103] Several long glass fiber reinforced polypropylene compositions were produced. The respective amounts of the components of the compositions are shown in Table 1.

[0104] Depending on the embodiment, one or two types of continuous glass multifilament strands are unwound from the package and transported to the impregnant coater. The impregnant (similar to the impregnant disclosed in WO2009 / 0808231) is melted and mixed at a temperature of 160°C and applied to the continuous glass multifilament strand unwound from the package by using the coater.

[0105] The continuous glass multifilament strand is subjected to an impregnation step in a single step.

[0106] The sheathing step was carried out directly in-line after the impregnation step at a temperature of about 250°C using a 75 mm twin screw extruder (manufactured by Berstorff with a screw UD ratio of 34) which fed the molten polypropylene matrix material and additives to the extruder head wire coating die. The sheathed strands were cut into pellets of 15 mm in length. The pellets were molded into appropriate shapes to measure a variety of properties as given in Table 2.

[0107] The uniformity of glass fiber distribution in the molded article is determined by the following method:

[0108] According to the conditions in the table below, 15 plates with a size of 310 mm × 270 mm × 3 mm were manufactured by injection molding pellets. The pellets have a black color due to the masterbatch. When the glass fiber is poorly dispersed, more glass fibers appear as "white spots" on the black plate on the surface of the plate. The number of white spots is counted and the average value of 15 plates is determined, which represents the degree of uneven distribution of glass fibers in the molded product.

[0109]

[0110] The tensile strength was measured according to ISO 527 / 1A (II) after conditioning at 23° C. for 7 days or at 120° C. for 7 days.

[0111] The isotropic tensile modulus was measured according to ISO 527 / 1 B (0°, 45°, 90°) after conditioning at 120°C for 7 days.

[0112] Free glass is measured by the following method:

[0113] With a suction pressure of 260 mbar, 1 kg of the resulting pellets are passed through a suction pipe of 2 m in length with 6 bends (180 degree bends) at 50 Hz. At the end of the suction pipe, a container and a filter having a pore size less than the fiber diameter are provided. The container receives the pellets, and the filter captures the free glass. The weight of the free glass present in the filter is measured and divided by the initial weight of the pellets, i.e. 1 kg, and the result represents the free glass.

[0114] Table 1

[0115] composition weight% GF1 and / or GF2 30.12 Impregnation agent 2.64 PP1 or PP2 63.42 Light Stabilizer 0.12 Antioxidants 0.4 Coupling agent 3 Masterbatch 0.3 total 100

[0116] PP1 is a propylene homopolymer with an MFI (ISO 1133-1:2011, 230°C / 2.16kg) of 50 dg / min.

[0117] PP2 is a propylene-ethylene copolymer with an ethylene content of 53 wt%, an MFI of 70 dg / min (ISO 1133-1:2011, 230°C / 2.16 kg).

[0118] GF1 was a standard size 30 roving SE4220 supplied by 3B as a roving package having a filament diameter of 12 μm and containing a sizing composition containing an aminosilane.

[0119] GF2 was standard size 30 roving SE4220, supplied by 3B as a roving package, having a filament diameter of 24 μm and containing a sizing composition containing an aminosilane.

[0120] The coupling agent is polypropylene grafted with maleic anhydride, trade name Exxelor 1020.

[0121] Table 2

[0122]

[0123] Using only glass multifilament strands with large diameters resulted in a large amount of free glass (Comparative Example 3, Comparative Example 6). Mixing glass multifilament strands with small diameters greatly reduced the free glass (Example 2, Example 5). The tensile strength and tensile modulus also became much higher with the mixture than with only glass multifilament strands with large diameters. The difference was particularly large after the samples were subjected to high temperatures.

[0124] By using glass multifilament strands with small diameters (Comparative Example 1, Comparative Example 4), further reduction of free glass and further improvement of tensile strength and tensile modulus were observed. However, white spots, i.e., unevenness of glass fiber distribution, became unacceptably high. Examples 2 and 5, which used two types of glass multifilament strands with different diameters, had a good balance of low free glass, high tensile properties, and low white spots.

Claims

1. A method for producing a glass fiber reinforced thermoplastic polymer composition, said method comprising the following sequential steps: a) unwinding at least one first continuous glass multifilament strand having a first filament thickness t1 from a first package and unwinding at least one second continuous glass multifilament strand having a second filament thickness t2 greater than the first filament thickness t1 from a second package, wherein t2 is at least 1 μm greater than t1, t1 is 1 to 45 μm, and t2 is 3 to 50 μm, and b) applying a sheath of a thermoplastic polymer composition around at least one first continuous glass multifilament strand and at least one second continuous glass multifilament strand to form a sheathed continuous multifilament strand comprising the at least one first continuous glass multifilament strand and the at least one second continuous glass multifilament strand. 2 . The method according to claim 1 , wherein t2 is 1 to 30 μm greater than t1 . The method according to claim 1 , wherein t2 is 5 to 20 μm greater than t1 .

4. The method according to any one of claims 1 to 3, wherein t1 is 2 to 40 μm.

5. The method according to any one of claims 1 to 3, wherein t1 is 3 to 30 μm.

6. The method according to any one of claims 1 to 3, wherein t1 is 5 to 20 μm.

7. The method according to any one of claims 1 to 3, wherein t1 is 10 to 15 μm.

8. The method according to any one of claims 1 to 3, wherein t2 is 5 to 45 μm.

9. The method according to any one of claims 1 to 3, wherein t2 is 10 to 40 μm.

10. The method according to any one of claims 1 to 3, wherein t2 is 15 to 35 μm.

11. The method according to any one of claims 1 to 3, wherein t2 is 20 to 30 μm.

12. The method of any one of claims 1-3, wherein the thermoplastic polymer composition comprises at least 80 wt% thermoplastic polymer.

13. The method of claim 12, wherein the thermoplastic polymer is a polyolefin.

14. The method according to claim 13, wherein the polyolefin is selected from the group of polypropylene or an elastomer of ethylene and an alpha-olefin comonomer having 4 to 8 carbon atoms, and any mixture thereof.

15. The method of any one of claims 1-3, wherein the thermoplastic polymer composition has a melt flow index of 20 to 150 dg / min measured according to ISO 1133-1:2011 at 2.16 kg / 230°C.

16. The method of any one of claims 1-3, wherein the thermoplastic polymer composition has a melt flow index of 25 to 120 dg / min measured according to ISO 1133-1:2011 at 2.16 kg / 230°C.

17. The method of any one of claims 1-3, wherein the thermoplastic polymer composition has a melt flow index of 35 to 100 dg / min measured according to ISO 1133-1:2011 at 2.16 kg / 230°C.

18. The method according to any one of claims 1 to 3, wherein the amount of glass is 10 to 70 wt% based on the sheathed continuous multifilament strand.

19. The method according to any one of claims 1 to 3, wherein the amount of glass is 25 to 70 wt% based on the sheathed continuous multifilament strand.

20. The method according to any one of claims 1-3, wherein the method further comprises, between steps a) and b), a step a1) of applying an impregnating agent to each of the continuous glass multifilament strands to which the sheath is applied in step b). 21 . The method according to claim 20 , wherein the amount of the impregnating agent in the sheathed continuous multifilament strand is 0.50 to 18 wt % based on the sheathed continuous multifilament strand.

22. The method according to claim 20, wherein the amount of the impregnating agent in the sheathed continuous multifilament strand is 0.50 to 15 wt% based on the sheathed continuous multifilament strand.

23. The method according to claim 20, wherein the amount of the impregnating agent in the sheathed continuous multifilament strand is 0.50 to 10 wt% based on the sheathed continuous multifilament strand.

24. The method of any one of claims 21-23, wherein the impregnating agent has a melting point at least 20°C lower than the melting point of the thermoplastic polymer composition and has a viscosity of 2.5 to 200 cSt at 160°C.

25. The method of claim 20, wherein the amount of the impregnated continuous multifilament strand is 10 to 70 weight % based on the sheathed continuous multifilament strand; and wherein the amount of the sheath is 30 to 90 weight % based on the sheathed continuous multifilament strand; and wherein the sum of the amounts of the impregnated continuous multifilament strand and the sheath is 100 weight %.

26. The method of claim 25, wherein the amount of the impregnated continuous multifilament strand is 25 to 70 wt% based on the sheathed continuous multifilament strand; and wherein the amount of the sheath is 30 to 75 wt% based on the sheathed continuous multifilament strand.

27. The method of any one of claims 1-3, wherein the method further comprises the step of cutting the sheathed continuous glass multifilament strand into pellets.

28. The method according to any one of claims 1 to 3, wherein Step a) comprises unwinding from a third package at least one third continuous glass multifilament strand having a third filament thickness t3, wherein t3 is different from t1 and t2, and Step b) includes applying the sheath around at least one third continuous glass multifilament, and the sheathed continuous multifilament strand further comprises the at least one third continuous glass multifilament.

29. Glass fiber reinforced thermoplastic polymer composition obtainable by the process according to any one of claims 1 to 28.

30. A glass fiber reinforced thermoplastic polymer composition comprising: A sheathed continuous multifilament strand comprising at least one first glass multifilament strand having a first filament thickness t1 and at least one second continuous glass multifilament strand having a second filament thickness t2 greater than the first filament thickness t1, and a sheath of a thermoplastic polymer composition provided around the at least one first continuous glass multifilament strand and the at least one second continuous glass multifilament, wherein t2 is at least 1 μm greater than t1, t1 is 1 to 45 μm, and t2 is 3 to 50 μm.

31. An article comprising the composition according to claim 29 or 30.

32. Use of a composition according to claim 29 or 30 for automotive applications.

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