Coated glass filament

Abstract

The present invention relates to a coated glass filament comprising a glass filament and a coating of a polypropylene composition provided directly on the glass filament wherein the polypropylene composition comprises A) a grafted polypropylene grafted with C1) a side chain compound capable of forming hydrogen bonds, and / or B) a non-grafted polypropylene and C2) a compound capable of forming hydrogen bonds, wherein the polypropylene composition comprises D) a low molecular weight polyethylene having a number average molecular weight of at most 5000 g / mol in an amount of less than 10% by weight, relative to the amount of the polypropylene composition, and wherein the total amount of A) and B) is at least 90% by weight, relative to the polypropylene composition.

Description

Technical Field

[0001] The present invention relates to coated glass filaments. The present invention also relates to multifilament strands comprising a plurality of such coated glass filaments. Background Art

[0002] Composites of glass filaments or fibers with polymers generally require high mechanical properties such as flexural and tensile moduli and strength. The mechanical properties of the composite are affected by the adhesion of the polymer to the glass fiber.

[0003] It is known to apply a sizing composition to the glass fiber before applying the polymer to improve the adhesion of the polymer to the glass fiber. Sizing compositions can generally be divided into aqueous systems and non-aqueous systems.

[0004] The use of an aqueous sizing composition requires a drying step. In practice, drying takes a large amount of time, and thus, dried fiber bobbins are prepared. From a practical point of view, aqueous sizing agents are preferred because they are easy to apply and do not require expensive equipment. However, in the case of aqueous sizing agents, drying takes time and energy because it is done in an oven, and in addition, when the glass is dried from the outside, this results in an uneven sizing agent content in the bobbin.

[0005] Non-aqueous sizing compositions do not have this problem associated with drying. US5998029 discloses a non-aqueous sizing agent for glass fibers, which comprises a film-forming agent miscible with the polymer to be reinforced and a silane coupling agent, the film-forming agent having a melting point of 30 - 60 °C and a viscosity of 75 - 400 cPs. In Examples IV and V, sizing agents for polypropylene glass fiber composites were prepared, which comprised VYBAR waxes having Mns of 1500 and 2600 as film-forming agents.

[0006] US20080292739 discloses a fiber product for forming a preform, which comprises heat-resistant continuous fibers coated with a thermoplastic sizing composition, the thermoplastic sizing composition comprising a thermoplastic material. In Example 2, a non-aqueous sizing composition based on a lower molecular weight modified polypropylene (molecular weight of about 6500 - 7000) was applied to continuous glass fibers during the manufacture of the continuous glass fibers. The modified polypropylene is a maleic anhydride functional structural moiety grafted onto a polypropylene chain. The modified polypropylene (35 wt%) was melt-blended with micro wax (65 wt%) to reduce and adjust the processing and application viscosity. The fibers to which the sizing composition was applied were gathered to form strands and then wound into packages.

[0007] Non-aqueous sizing compositions are less preferred because they are not easily commercially available due to the high cost of the raw materials. Summary of the Invention

[0008] An object of the present invention is to provide a coated glass fiber in which the above and / or other problems are solved.

[0009] Accordingly, the present invention provides a coated glass fiber comprising a glass fiber and a coating of a polypropylene composition provided directly on the glass fiber, wherein the polypropylene composition comprises

[0010] A) grafted polypropylene grafted with C1) a side chain compound capable of forming hydrogen bonds, and / or

[0011] B) non-grafted polypropylene and C2) a compound capable of forming hydrogen bonds,

[0012] wherein the polypropylene composition comprises D) low molecular weight polyethylene in an amount of less than 10% by weight relative to the polypropylene composition, preferably a low molecular weight polyolefin having a number average molecular weight of at most 5000 g / mol.

[0013] The present invention also provides a coated glass fiber comprising a glass fiber and a coating of a polypropylene composition provided directly on the glass fiber, wherein the polypropylene composition comprises

[0014] A) grafted polypropylene grafted with C1) a side chain compound capable of forming hydrogen bonds, and / or

[0015] B) non-grafted polypropylene and C2) a compound capable of forming hydrogen bonds,

[0016] wherein the total amount of A) and B) is at least 90% by weight relative to the polypropylene composition,

[0017] wherein the polypropylene composition comprises D) low molecular weight polyethylene having a number average molecular weight of at most 5000 g / mol in an amount of less than 10% by weight, less than 5.0% by weight, less than 3.0% by weight, less than 1.0% by weight, less than 0.5% by weight or 0% by weight relative to the amount of the polypropylene composition.

[0018] The coated glass fiber according to the present invention can be in the form of a single glass fiber provided with a coating. In this case, the coating can be provided on substantially all or part of the surface of the glass fiber. The coated glass fiber can be in the form of a plurality of glass fibers (partially) bundled together. In this case, the coating may not be present on the portions of the glass fibers in contact with each other.

[0019] In some preferred embodiments, the glass filaments provided with a coating thereon have been obtained by recycling polymer-coated glass filaments such as epoxy resin-coated chopped glass filaments. The polymer such as epoxy resin can be removed from the polymer-coated glass filaments, for example, by burning off the polymer to obtain uncoated glass filaments. The coating of the polypropylene composition can be directly provided on the uncoated glass filaments thus obtained to obtain the coated glass filaments according to the present invention. In view of the increasing awareness of sustainability, the use of recycled materials is highly desirable.

[0020] The coated glass filaments according to the present invention comprise a coating of a polypropylene composition directly provided on the glass filaments. Herein, the term "directly provided" is understood to mean that the polypropylene composition is in direct contact with the filaments, i.e., there is no component between the filament surface and the coating, and thus this means that there is no adhesion promoter, sizing agent or similar compound between the polymer composition and the filaments. Therefore, it will be appreciated that the "glass filaments" on which the coating is directly provided are glass filaments that have not been provided with another coating of an adhesion promoter or sizing agent.

[0021] Since there is no sizing composition, the problems associated with the sizing composition are solved.

[0022] The polypropylene composition used according to the present invention comprises C1) a side chain compound capable of forming hydrogen bonds (as part of the grafted polypropylene) and / or C2) a compound capable of forming hydrogen bonds. The presence of C1) and / or C2) in the polypropylene composition improves the adhesion to the glass fibers. Compounds C1) and C2) have a hydrogen atom or a functional group that generates a hydrogen atom through (partial) hydrolysis of the functional group, which is capable of forming hydrogen bonds with the glass filaments. The hydrogen bonds improve the adhesion of the polypropylene composition to the glass filaments. In some cases, in addition to forming hydrogen bonds, a condensation reaction between the silanol groups on the glass surface and the hydrogen atoms can produce ester bonds or ether bonds and thus result in covalent bonds with the glass surface.

[0023] Preferably, the polypropylene composition comprises

[0024] -A) grafted polypropylene grafted with a side chain compound C1) selected from acid anhydrides (such as maleic anhydride, itaconic anhydride), vinyl oligosilanes, acryloyloxy oligosilanes, epoxy (meth)acrylates and combinations thereof;

[0025] -A) grafted polypropylene grafted with a side chain compound C1) selected from acid anhydrides (such as maleic anhydride, itaconic anhydride), vinyl oligosilanes, acryloyloxy oligosilanes, epoxy (meth)acrylates and combinations thereof, and

[0026] B) non-grafted polypropylene;

[0027] -A) Grafted polypropylene grafted with a side chain compound selected from C1) acid anhydrides (such as maleic anhydride, itaconic anhydride), vinyl oligosilanes, acryloyloxy oligosilanes, epoxy (meth)acrylates, and combinations thereof,

[0028] B) Ungrafted polypropylene, and

[0029] C2) A compound selected from oligosilanes (such as vinyl oligosilanes, aminopropyl oligosilanes, acryloyloxy oligosilanes), copolymers of ethylene and 2-hydroxyethyl methacrylate, epoxy (meth)acrylates, polyamides, organometallic compounds having pyrophosphate groups, and combinations thereof; or

[0030] -B) Ungrafted polypropylene, and

[0031] C2) A compound selected from vinyl oligosilanes, acryloyloxy oligosilanes, copolymers of ethylene and 2-hydroxyethyl methacrylate, epoxy (meth)acrylates, organometallic compounds having pyrophosphate groups, and combinations thereof.

[0032] A) Grafted polypropylene

[0033] The polypropylene composition used according to the present invention may contain grafted polypropylene. The grafted polypropylene is polypropylene grafted with a side chain compound C1) capable of forming hydrogen bonds.

[0034] Suitable examples of C1) include acid anhydrides (such as maleic anhydride, itaconic anhydride), oligosilanes (such as vinyl oligosilanes, aminopropyl oligosilanes, acryloyloxy oligosilanes), epoxy (meth)acrylates, polyamides, and combinations thereof. Those skilled in the art know how to obtain A) by grafting C1) onto polypropylene. When C1) is maleic anhydride, the double bond of maleic anhydride is consumed to achieve grafting and form a succinic anhydride bond with polypropylene.

[0035] An example of the epoxy (meth)acrylate is glycidyl methacrylate.

[0036] Preferably, C1) includes acid anhydrides (such as maleic anhydride, itaconic anhydride). Most preferably, C1) includes maleic anhydride. This results in good adhesion between the polypropylene composition and glass fibers.

[0037] Preferably, the amount of C1) is 0.5 to 10% by weight relative to the amount of A), such as 0.6 to 5.0% by weight, 0.7 to 3.0% by weight, 0.8 to 2.0% by weight.

[0038] C2) Compounds capable of forming hydrogen bonds

[0039] The polypropylene composition used according to the present invention may comprise B) ungrafted polypropylene and C2) a compound capable of forming hydrogen bonds. Preferably, C2) has an unsaturated group capable of reacting with ungrafted polypropylene to form hydrogen bonds, or C2) has a hydrophobic group (such as a copolymer of ethylene and 2-hydroxyethyl methacrylate (PE-HEMA)).

[0040] Suitable examples of C2) include oligosilanes (such as vinyl oligosilanes, aminopropyl oligosilanes, acryloyloxy oligosilanes), a copolymer of ethylene and 2-hydroxyethyl methacrylate (PE-HEMA), epoxy (meth)acrylates, polyamides, organometallic compounds having pyrophosphate groups, and combinations thereof.

[0041] When the polypropylene composition comprises A), C2) is preferably a compound selected from oligosilanes (such as vinyl oligosilanes, aminopropyl oligosilanes, acryloyloxy oligosilanes), a copolymer of ethylene and 2-hydroxyethyl methacrylate (PE-HEMA), epoxy (meth)acrylates, polyamides, organometallic compounds having pyrophosphate groups, and combinations thereof.

[0042] When the polypropylene composition does not comprise A), C2) is preferably a compound selected from vinyl oligosilanes, acryloyloxy oligosilanes, a copolymer of ethylene and 2-hydroxyethyl methacrylate, epoxy (meth)acrylates, organometallic compounds having pyrophosphate groups, and combinations thereof.

[0043] Preferably, C2) is selected from oligosilanes (such as vinyl oligosilanes, aminopropyl oligosilanes, acryloyloxy oligosilanes), organometallic compounds having pyrophosphate groups, and combinations thereof. This results in good adhesion between the polypropylene composition and the glass fibers.

[0044] Preferably, C2) comprises a vinyl oligosilane or an acryloyloxy oligosilane, more preferably a vinyl oligosilane. This results in particularly good adhesion between the polypropylene composition and the glass fibers.

[0045] It has been found that the oligosilane has a low enough volatility to react with the polypropylene to achieve the desired effect.

[0046] Preferably, the polypropylene composition does not contain or substantially does not contain alkoxysilane compounds having a molecular weight of less than 300 (such as γ-aminopropyltriethoxysilane (APTES), γ-glycidoxypropyltrimethoxysilane (GPTMS), γ-methacryloxypropyltrimethoxysilane (MPTMS), vinyltriethoxysilane (VTES)). Preferably, the amount of such alkoxysilane compounds having a molecular weight of less than 300 is less than 10% by weight, less than 5.0% by weight, less than 3.0% by weight, less than 1.0% by weight, less than 0.5% by weight or 0% by weight based on the polypropylene composition.

[0047] Preferably, C2) comprises an organometallic compound having a pyrophosphate group, preferably a titanate pyrophosphate compound or a zirconate pyrophosphate compound. This results in particularly good adhesion between the polypropylene composition and the glass fibers. Suitable examples include neopentyl(diallyl)oxytris(dioctyl)pyrophosphato titanate, cyclo(dioctyl)pyrophosphate dioctyl titanate, dicyclo(dioctyl)pyrophosphate titanate, neopentyl(diallyl)oxytris(N-ethylenediamino)ethyl titanate, cyclo[bis(neopentyl(diallyl))]pyrophosphato bis(neopentyl(diallyl)) zirconate, bis(dioctyl)pyrophosphate oxoethyl titanate and the 2-(N,N-dimethylamino)isobutanol adduct of bis(dioctyl)pyrophosphate oxoethyl titanate.

[0048] Preferably, the amount of C2) is 0.2 to 10% by weight, such as 0.3 to 5.0% by weight, 0.4 to 3.0% by weight, 0.5 to 2.0% by weight based on the total amount of B) and C2).

[0049] D) Low molecular weight polyolefins

[0050] The polypropylene composition comprises an amount of D) low molecular weight polyethylene having a number average molecular weight of at most 5000 g / mol of less than 10% by weight based on the polypropylene composition. It will be appreciated that this includes the case where the polypropylene composition does not contain D) low molecular weight polyethylene having a number average molecular weight of at most 5000 g / mol. If the polypropylene composition contains D) low molecular weight polyethylene having a number average molecular weight of at most 5000 g / mol, its amount is less than 10% by weight based on the polypropylene composition. Thus, this feature can also be expressed as "the amount of D) low molecular weight polyethylene having a number average molecular weight of at most 5000 g / mol in the polypropylene composition is less than 10% by weight based on the polypropylene composition".

[0051] Preferably, the polypropylene composition does not contain or substantially does not contain low molecular weight polyethylene having a number average molecular weight of at most 5000 g / mol. Preferably, the amount of such low molecular weight polyethylene relative to the polypropylene composition is less than 10 wt%, less than 5.0 wt%, less than 3.0 wt%, less than 1.0 wt%, less than 0.5 wt% or 0 wt%.

[0052] Preferably, the polypropylene composition does not contain or substantially does not contain low molecular weight polyethylene having a number average molecular weight of at most 5000 g / mol. Preferably, the amount of such low molecular weight polyolefin (the sum of low molecular weight polyethylene having a number average molecular weight of at most 5000 g / mol and any other polyolefin having a number average molecular weight of at most 5000 g / mol) relative to the polypropylene composition is less than 10 wt%, less than 8.0 wt%, less than 5.0 wt%, less than 3.0 wt%, less than 1.0 wt%, less than 0.5 wt% or 0 wt%.

[0053] Additive

[0054] The polypropylene composition may additionally contain additives such as flame retardants, pigments, lubricants, slip agents, flow promoters, antistatic agents, processing stabilizers, long-term stabilizers and / or UV stabilizers. The amount of the additives may be, for example, 0.1 to 5.0 wt%.

[0055] Preferably, the total amount of A), B), C2), D) and the additives is 100 wt% relative to the polypropylene composition.

[0056] Preferred composition

[0057] Preferably, the polypropylene composition has a melt viscosity of at most 25 Pa·s at the melting temperature of the polymer composition, preferably in the range of 1.0 to 25 Pa·s, more preferably in the range of 1.0 to 20 Pa·s, even more preferably in the range of 1.8 to 19.4 Pa·s or in the range of 1.0 to 15 Pa·s, even more preferably in the range of 1.0 to 10 Pa·s, and most preferably 1.0 to 5.0 Pa·s, where the melting temperature of the polymer composition is determined for a 5 mg sample on the second heating curve using differential scanning calorimetry with heating and cooling rates of 10 °C / min and where the melt viscosity is determined according to ISO6721-10:2015 by applying oscillatory shear to the molten sample at an angular frequency of 1 rad / s and a shear strain of 5%.

[0058] In some preferred embodiments, the amount of A) is at least 50 wt%, at least 60 wt%, at least 70 wt%, at least 80 wt%, at least 90 wt%, at least 95 wt%, at least 98 wt%, at least 99 wt% or 100 wt% based on the polypropylene composition.

[0059] In some preferred embodiments, the total amount of B) and C2) is at least 50 wt%, at least 60 wt%, at least 70 wt%, at least 80 wt%, at least 90 wt%, at least 95 wt%, at least 98 wt%, at least 99 wt% or 100 wt% based on the polypropylene composition.

[0060] In some preferred embodiments, the polypropylene composition comprises A) and B). Preferably, the total amount of A) and B) is at least 70 wt%, at least 80 wt%, at least 90 wt%, at least 93 wt%, at least 95 wt%, at least 97 wt%, at least 99 wt% or 100 wt% based on the polypropylene composition. Preferably, the amount of A) is 1.0 to 30 wt% based on the total amount of A) and B), such as 2.0 to 25 wt%, 3.0 to 20 wt% or 4.0 to 10 wt%.

[0061] In some preferred embodiments, the polypropylene composition comprises A), B) and C2). Preferably, the amount of B) is at least 65 wt% based on the total amount of A), B) and C2). Preferably, the amount of A) is 1.0 to 30 wt% based on the total amount of A) and B), such as 2.0 to 25 wt%, 3.0 to 20 wt% or 4.0 to 10 wt%. Preferably, the amount of C2) is 0.2 to 10 wt% based on the total amount of B) and C2), such as 0.3 to 5.0 wt%, 0.4 to 3.0 wt%, 0.5 to 2.0 wt%. In a particularly preferred embodiment, based on the total amount of A), B) and C), the amount of A) is 1.0 to 5.0 wt%, the amount of B) is 90 to 98 wt%, and the amount of C) is 1.0 to 5.0 wt%.

[0062] In a particularly preferred embodiment, wherein the polypropylene composition comprises A), B) and C2), C1) is selected from acid anhydrides (such as maleic anhydride, itaconic anhydride) and C2) comprises an organometallic compound having a pyrophosphate group, preferably a titanate pyrophosphate compound or a zirconate pyrophosphate compound.

[0063] Other aspects

[0064] The present invention also provides a multifilament strand, which comprises a plurality of coated glass filaments according to the present invention in a bundle. The multifilament strand may additionally comprise uncoated glass filaments, but preferably at least 50 wt%, at least 60 wt%, at least 70 wt%, at least 80 wt%, at least 90 wt%, at least 95 wt%, at least 98 wt%, at least 99 wt% of the multifilament strand is the coated glass filament according to the present invention.

[0065] The present invention also provides pellets of a glass fiber reinforced thermoplastic polymer composition comprising a sheathed continuous multifilament strand, the sheathed continuous multifilament strand comprising a core extending longitudinally and a polymer sheath tightly surrounding the core, wherein the core comprises the glass multifilament strand according to the present invention.

[0066] The length of the glass filaments in the pellets may be substantially the same as the pellet length, 10 to 55 mm, preferably 10 to 40 mm, more preferably 10 to 30 mm and most preferably 10 to 20 mm. Such pellets can be obtained by applying a polymer sheath of a thermoplastic polymer composition comprising a polyolefin around the core and cutting the sheathed continuous multifilament strand, as described for example in WO2009080281A1 and WO2022128783A1.

[0067] In the pellets, the amount of the glass filaments may be, for example, 60 to 95 wt% relative to the pellets, such as 70 to 90 wt%.

[0068] It should be noted that the present invention relates to the subject matter defined by the independent claims alone or in combination with any possible combinations of the features described herein, preferably in particular those combinations of the features presented in the claims. Thus, it is to be understood that all combinations of features relating to the compositions according to the present invention, all combinations of features relating to the methods according to the present invention, and all combinations of features relating to the compositions according to the present invention and features relating to the methods according to the present invention are described herein.

[0069] It should be further noted that the terms 'comprising', 'including', 'containing' do not exclude the presence of other elements. However, it is also to be 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 as it provides a simpler and more economical method for preparing the product / composition. Similarly, it is also to be 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 as it provides a simpler and more economical method.

[0070] The present invention is now illustrated by means of the following examples, but the present invention is not limited thereto.

[0071] Experiment

[0072] Samples of the polymer composition were prepared from the components in Table 1 as follows: If all components are solids, a powder blend was made by mixing the powders in a plastic bag, and the polymer in pellet form was powdered by cryogenic grinding. In the case of liquid additives, the additive was dissolved in a suitable solvent, spread on powdered polypropylene (PP), and the solvent was allowed to evaporate overnight in a fume hood, after which the powder with the additive was well mixed by shaking in a plastic bag.

[0073] The mixture thus formed was added at 300 g / h by means of a loss-in-weight feeder to a Thermo Scientific Process 11 (P11) 11 mm diameter, twin-screw, co-rotating extruder with a screw equipped with conveying elements and 3 sections of kneading elements, and a barrel with 8 heating zones set at 40, 120, 180, 200, 200, 200 and 200 °C, and the die set at 200 °C. The extrudate was cooled in a water bath with flowing tap water and pelletized.

[0074] IFSS measurement (Interfacial Shear Strength)

[0075] Samples of coated glass fibres were prepared from the pellets and the interfacial shear strength was determined by the Microbond test described in L. Yang & J. L. Thomason: Development and application of micromechanical techniques for characterising interfacial shear strength (IFSS) in fibre-thermoplastic composites - Polymer Testing 31 (2012) 895 - 903. The pellets of the composition obtained above were melted and fibres were drawn from the melt. Loose knots were made from the fibres and a glass fibre was placed in the loose knot. The knot was tightened and the excess PP fibres were cut off, resulting in a small knot of PP fibres around the glass fibre. It was heated under nitrogen to melt the PP composition and droplets of the PP composition were formed around the fibre. After cooling, the droplets solidified. The glass fibre was pulled out to determine the interfacial shear strength.

[0076] In CE1, the polymer composition was applied to glass fibres provided with an aminosilane sizing composition optimized for adhesion to PP. In CE2 - CE4, E5, RE6 - RE7, E8 - E19, the polymer composition was applied to glass fibres provided by Fibrecoat GmbH without any sizing composition.

[0077] Materials:

[0078] A)

[0079] C1) MAH type: Exxelor PO1020, from Exxon Mobil, polypropylene grafted with maleic anhydride (0.9 wt% anhydride)

[0080] C1) ITA type: Scona TSPP 8219GA, from BYK Chemie GmbH, polypropylene grafted with itaconic anhydride (2 wt% anhydride)

[0081] C1) Epoxide type: Scona TPPP 8104FA, from Chemie GmbH, polypropylene grafted with glycidyl methacrylate (2.5 wt% glycidyl methacrylate)

[0082] B)

[0083] PP595A, from SABIC, propylene homopolymer with an MFR of 47 dg / min according to ISO1133 at 230 °C and 2.16 kg

[0084] C2)

[0085] PA: Radipol S24HA, from Radicii Group, polyamide 6

[0086] PE-HEMA: poly(ethylene-hydroxyethyl methacrylate), containing 12 wt% of hydroxyethyl methacrylate

[0087] Vinyl oligosilane: Silquest G-170, from Momentive Performance Materials

[0088] Aminopropyl oligosilane: Silquest VX-225, from Momentive Performance Materials

[0089] Acryloxy oligosilane: Silquest A-274, from Momentive Performance Materials

[0090] Titanate pyrophosphate: Ken-React LICA 38, from Kenrich Petrochemicals, Inc., neopentyl (diallyl) oxy tris(dioctyl) pyrophosphate titanate

[0091] The compounds mentioned as C2) above have hydrogen atoms capable of forming hydrogen bonds or functional groups that generate hydrogen atoms through (partial) hydrolysis of the functional groups.

[0092] Others

[0093] EVA: Poly(ethylene-vinyl acetate), containing 10 wt% vinyl acetate

[0094] Zirconate phosphate: Ken-React ZN 12, from Kenrich Petrochemicals, Inc., isooctyl hydrogen phosphate zirconium complex

[0095] The compounds mentioned as others above do not have hydrogen atoms capable of forming hydrogen bonds, nor do they have functional groups that generate hydrogen atoms through (partial) hydrolysis of the functional groups.

[0096] Other measurement methods

[0097] Melt viscosity

[0098] The melt viscosity is measured according to ISO6721-10:2015 on pellets or extrudates in an inserted plate-plate oscillatory shear rheometer. Use an MCR 502 rotational rheometer from AntonPaar. The sample is melted within a 25 mm diameter test geometry at the measurement temperature (oven set to 250 °C or 290 °C), and the sample is preheated in the oven for 1 minute to obtain a completely melted sample and trimmed to a 1 mm gap, after which oscillatory shear is applied at an angular frequency of 1 rad / s and a shear strain of 5%. During this test, the melt viscosity is monitored as a function of time.

[0099] Standard linear propylene homopolymers with different melt flow rates are used to calibrate the rheometer.

[0100] Melting temperature

[0101] The melting temperature is determined by differential scanning calorimetry using a second heating curve, where the first heating rate is 10 °C / min, the first cooling rate is 10 °C / min, the second heating rate is 10 °C / min, and the sample weight is 5 mg.

[0102] Mn and Mw

[0103] At 160 °C, 5 mg of the sample is dissolved in 10 ml of 1,2,4-trichlorobenzene. The vial is placed in a Polymer Char GPC and automatically processed.

[0104] The following key parameters are applied:

[0105] · Chromatography: PolymerChar GPC-IR system operating at 160 °C

[0106] · Detection: Polymer Char IR5 infrared detector; PolymerChar viscometer

[0107] · Use the IR5 as a concentration detector.

[0108] · Column set: Three Polymer Laboratories 13μm PLgel Olexis, 300 x 7.5 mm

[0109] · Calibrate the PE molar mass with linear PE standards (narrow and broad (Mw / Mn = 4 to 15)) in the range of 0.5 - 2800 kg / mol

[0110] · The concentration of the injected sample is 0.03% m / m, stabilized with Irgafos 168 and Topanol CA (sample: Irgafos: Topanol weight ratio = 1:1:1)

[0111] · The solvent and eluent are 1,2,4-trichlorobenzene stabilized with 1 g / L BHT.

[0112] Table 1

[0113]

[0114] In CE1, the glass fiber with a sizing composition coated with a composition containing polypropylene grafted with maleic anhydride results in a high IFSS.

[0115] CE2 shows that applying polypropylene to the glass fiber without a sizing composition results in a low IFSS of less than 10 MPa.

[0116] The comparison of CE3 to CE4 with CE2 shows that using a compound that does not have a hydrogen atom capable of forming a hydrogen bond and does not have a functional group that generates a hydrogen atom through (partial) hydrolysis of the functional group still results in a low IFSS of less than 10 MPa.

[0117] The comparison of E5, RE6, RE7 and E8 to E19 with CE2 shows that using a compound that has a hydrogen atom capable of forming a hydrogen bond or has a functional group that generates a hydrogen atom through (partial) hydrolysis of the functional group results in a high IFSS of more than 10 MPa.

[0118] The ILSS of bare glass filaments with respect to pure anhydride-grafted PP is very high (E5 and E11), even exceeding that of glass filaments sized with PP / PP-g-MAH 97 / 3 resin (CE1). Diluting PP-g-MAH in the PP homopolymer decreased the ILSS value (E13 - E15), but even at 3 wt% PP-g-MAH dilution (E13) still resulted in a relatively high ILSS. The effect of epoxy-grafted PP was lower than that of anhydride-grafted PP (E12 vs. E4 and E11).

[0119] Adding oligosilanes to PP resulted in high ILSS (E8 and E10 vs. CE2). When comparing different types of oligosilanes, aminopropyl oligosilane in combination with PPMAH (E18) had the lowest effect. Acryloxy oligosilane (E19) had a slightly higher effect and vinyl oligosilane (E10) had a much higher effect. Increasing the vinyl oligosilane level to 8 wt% resulted in a slight increase (E8)

[0120] Adding both oligosilanes and grafted PPMAH to PP had no major effect on ILSS. The addition of both resulted in a lower ILSS than the addition of either one alone (E17 vs. E10, E17 vs. E13).

[0121] Adding titanate pyrophosphate resulted in high ILSS (E9 vs. CE2). Adding both titanate pyrophosphate and grafted PPMAH to PP resulted in a large increase in ILSS. The addition of both resulted in a higher ILSS than the addition of either one alone (E16 vs. E9, E16 vs. E13).

[0122] Specific interactions via alcohol or amine / amide groups resulted in higher ILSS values, but still at the lower end of all the tested samples (RE6 and RE7).

Claims

1. A coated glass fiber, comprising a glass fiber and a coating of a polypropylene composition directly provided on the glass fiber, wherein the polypropylene composition comprises A) grafted polypropylene grafted with C1) a side chain compound capable of forming hydrogen bonds, and / or B) non-grafted polypropylene and C2) a compound capable of forming hydrogen bonds, wherein the polypropylene composition comprises an amount of D) low molecular weight polyethylene having a number average molecular weight of at most 5000 g / mol of less than 10% by weight relative to the polypropylene composition, wherein the total amount of A) and B) is at least 90% by weight relative to the polypropylene composition.

2. The coated glass fiber according to claim 1, wherein the polypropylene composition comprises A) and B).

3. The coated glass fiber according to any one of the preceding claims, wherein the polypropylene composition comprises B) and C2).

4. The coated glass fiber according to any one of the preceding claims, wherein the polypropylene composition comprises A), B) and C2).

5. The coated glass fiber according to any one of the preceding claims, wherein C1) is selected from acid anhydrides (such as maleic anhydride, itaconic anhydride), vinyl oligosilanes, acryloyloxy oligosilanes, epoxy (meth)acrylates and combinations thereof.

6. The coated glass fiber according to any one of the preceding claims, wherein C1) is selected from acid anhydrides (such as maleic anhydride, itaconic anhydride), preferably C1) comprises maleic anhydride.

7. The coated glass fiber according to any one of the preceding claims, wherein C2) is selected from oligosilanes (such as vinyl oligosilanes, aminopropyl oligosilanes, acryloyloxy oligosilanes), copolymers of ethylene and 2-hydroxyethyl methacrylate, epoxy (meth)acrylates, polyamides, organometallic compounds having pyrophosphate groups and combinations thereof, wherein in the absence of C1), C2) is selected from vinyl oligosilanes, acryloyloxy oligosilanes, copolymers of ethylene and 2-hydroxyethyl methacrylate, epoxy (meth)acrylates, organometallic compounds having pyrophosphate groups and combinations thereof.

8. The coated glass fiber according to any one of the preceding claims, wherein C2) is selected from vinyl oligosilanes, acryloyloxy oligosilanes, organometallic compounds having pyrophosphate groups and combinations thereof, Preferably, wherein C2) comprises vinyl oligosilane, and / or C2) comprises an organometallic compound having a pyrophosphate group, preferably a titanate pyrophosphate compound or a zirconate pyrophosphate compound.

9. The coated glass filaments according to any one of the preceding claims, wherein the polypropylene composition comprises A), B) and C2), wherein C1) is selected from acid anhydrides (such as maleic anhydride, itaconic anhydride), and C2) comprises an organometallic compound having a pyrophosphate group, preferably a titanate pyrophosphate compound or a zirconate pyrophosphate compound.

10. The coated glass filaments according to any one of the preceding claims, wherein the polypropylene composition comprises an alkoxysilane compound having a molecular weight of less than 300 (such as γ-aminopropyltriethoxysilane (APTES), γ-glycidoxypropyltrimethoxysilane (GPTMS), γ-methacryloxypropyltrimethoxysilane (MPTMS), vinyltriethoxysilane (VTES)) in an amount of less than 10% by weight based on the polypropylene composition.

11. The coated glass filaments according to any one of the preceding claims, wherein the total amount of A) and B) is at least 93% by weight, at least 95% by weight, at least 97% by weight, at least 99% by weight or 100% by weight based on the polypropylene composition.

12. The coated glass filaments according to any one of the preceding claims, wherein the amount of C1 is 0.5 to 10% by weight based on the amount of A), such as 0.6 to 5.0% by weight, 0.7 to 3.0% by weight, 0.8 to 2.0% by weight, and / or the amount of C2 is 0.2 to 10% by weight based on the total amount of B) and C2), such as 0.3 to 5.0% by weight, 0.4 to 3.0% by weight, 0.5 to 2.0% by weight.

13. The coated glass filaments according to any one of the preceding claims, wherein the glass filaments are obtained by removing a polymer from polymer-coated glass filaments, such as epoxy resin-coated chopped glass filaments, preferably wherein removing the polymer comprises burning off the polymer.

14. A multifilament strand comprising a bundle of a plurality of coated glass filaments according to any one of claims 1 to 12.

15. A pellet of a glass fiber-reinforced thermoplastic polymer composition comprising a sheathed continuous multifilament strand, the sheathed continuous multifilament strand comprising a core extending longitudinally and a polymer sheath tightly surrounding the core, wherein the core comprises the glass multifilament strand according to claim 14.

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