WO2024099922A1

WO2024099922A1 - Glass fiber reinforced thermoplastic composition with improved impact resistance

Info

Publication number: WO2024099922A1
Application number: PCT/EP2023/080756
Authority: WO
Inventors: Robert Russell Gallucci; Tariq Ali SYED; Robert Maria Martin DONNERS; Angel YANEV; Remco Bos; Liang Wen
Original assignee: Sabic Global Technologies B.V.
Priority date: 2022-11-07
Filing date: 2023-11-06
Publication date: 2024-05-16

Abstract

The present invention relates to a glass fiber (GF) reinforced thermoplastic composition, its production and its use. The thermoplastic composition of the present invention has improved impact performance and/or improved strength.

Description

Glass fiber reinforced thermoplastic composition with improved impact resistance

The present invention relates to a glass fiber (GF) reinforced thermoplastic composition, further to a process for producing a glass fiber reinforced thermoplastic composition, as well as to the use of the glass fiber reinforced thermoplastic composition to produce an article, and a process to produce an article from the thermoplastic composition. The article can be used in various fields, such as in automotive interior and exterior applications.

Introduced more than a half century ago, fiber-reinforced plastics are composite materials with a wide range of applications in industry, for example in the aerospace, automotive, shipping, building and construction industries. The term "composite" can apply to any combination of individual materials, for example to a thermoplastic polymer (the matrix) in which fibers (reinforcing filler) have been dispersed. A great diversity of organic fibers, including synthetic fibers such as polyamide, polytetrafluoroethylene, polyesters, natural fibers, such as cotton, hemp, flax, jute; and inorganic fibers, such as glass fibers and carbon fibers are often used as reinforcements in composite materials.

The reinforced plastics industry has been using glass fibers in different forms for reinforcing polymer matrices to produce a diversity of products. Glass fibers are generally supplied as a plurality of continuous, very long filaments, and can be in the form of strands, rovings or yarns. A filament is an individual fiber of reinforcing material. A strand is a plurality of bundled filaments. Yarns are collections of filaments or strands twisted together. A roving refers to a collection of strands wound into a package.

In the production of short glass fiber compositions or compounds, chopped strands of pre-determined length are mixed with a thermoplastic polymer in an extruder, during which the integrity of the glass fiber strands is destroyed and the glass fibers are dispersed throughout the molten thermoplastic polymer. Due to fiber breakage, the fiber length is decreased during this process, typically to well below 1 mm. The obtained compound is formed into pellets. These pellets are consecutively supplied to an injection moulding or compression-moulding machine and formed into moulded articles.

Long glass fiber (LGF) reinforced thermoplastic polymer compositions -optionally in the form of, for example, pellets or granules- are also being used in industry because they possess excellent mechanical strength, heat resistance and formability. Long glass fiber-reinforced compositions are generally prepared by a sheathing or wire-coating process, by crosshead extrusion or several pultrusion techniques. Using these technologies, impregnated or coated fiber strands are formed; these may then be cut into lengths, the pellets or granules thus obtained being suitable for further processing, i.e. for injection moulding and compression moulding as well as for extrusion compression moulding processes, into (semi)-finished articles. Long glass fiber-reinforced polymer compositions contain glass fibers having a length of at least 1 mm, often at least 2 mm and typically between 5 and 20 mm. As a result, glass fibers in moulded articles made from long glass fiber-reinforced polymer compositions generally are of higher length than in articles made from short glass fiber compositions, resulting in better mechanical properties.

While long glass fiber reinforced thermoplastics are very useful, they are still deficient in the strength and impact of metal parts they often try to replace (especially in vehicles where the LGF part with lighter weight is highly desired). Therefore, there exists a need for LGF parts with improved mechanical properties.

Initial processes to make LGF materials involved dispersing/spreading a continuous glass roving into its individual filaments and more or less coating each individual fiber with molten resin. The coated filaments were then consolidated and chopped into the LGF pellets. Such various processes worked well and gave very good fiber-resin contact. However, the rate at which this more or less individual filament coating could be achieved was rather slow. An improved wire coating LGF process was developed wherein the glass roving was not dispersed into individual filaments but covered as a bundle of filaments with a modified thermoplastic formulation much as multiple strands of copper wire would be coated by a plastic insulator to make cable. Some of the glass fiber in the interior of such a "wire coated" LGF bundle would not be in contact with the modified resin. Full glass wet out and dispersion would be achieved in the molding operation through melt mixing and the effect of the special resin modification for example as described in EP 2,219,839.

EP 2,219,839 discloses a process for producing a LGF reinforced thermoplastic composition, comprising the subsequent steps of unwinding at least one continuous glass multifilament strand, applying 0.5 to 20% by mass of an impregnating agent to the strand, and applying a sheath of thermoplastic polymer around the strand. The impregnating agent is for example a highly branched poly (alpha-olefin), in particular a highly branched polyethylene wax.

The benefit of this wire coating LGF process was much faster line speed with more efficient and lower cost in manufacturing. However relying on full glass fiber (GF) dispersion in the molding process is not completely successful, developing better GF resin adhesion with better mechanical properties in the lower cost wire coating LGF is desired.

The present invention has found that an addition of EVA (Ethylene Vinyl Acetate) wax to the composition results in better impact performance and/or higher strength than conventionally using a polyolefin wax alone, likely by improving GF and polymer matrix interaction through better bonding of the polar LGF and the non-polar polymer matrix.

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%".

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.

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.

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.

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".

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 together to form a new range. For example, when it is described in the context that an amount of a certain component is at least lwt%, preferably at least 2wt%, and at most 5%, preferably at most 4wt%, being in one example specifically 3wt%, then the amount ranges of l-2wt%, 2-3wt%, 3-4wt%, 4-5wt%, l-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 l-5wt%, preferably 2- 4wt%, being in one example specifically 3wt%, then the amount ranges of l-2wt%, 2-3wt%, 3-4wt%, 4- 5wt%, etc, are all inherently disclosed, as if they were explicitly described in the present invention.

Glass fiber-reinforced thermoplastic composition

In one aspect of the present invention, there is provided a glass fiber-reinforced thermoplastic composition. The glass fiber-reinforced thermoplastic composition comprises, based on a total weight thereof:

(a) 30-90 wt% of a thermoplastic polymer matrix,

(b) 10-70 wt% of glass fibers, and

(c) 0.5-20 wt% of an impregnating composition comprising or consisting of:

(cl) at least one impregnating agent which is non-volatile, has a melting point of at least 20°C below the melting point of the thermoplastic polymer matrix, has a viscosity of from 2.5 to 100 cS at application temperature, and is compatible with the thermoplastic polymer matrix, and

(c2) at least one EVA (ethylene vinyl acetate) wax, in an amount of 5-99 wt% based on the total weight of the impregnating composition.

In some instances, the thermoplastic composition further comprises:

(d) 5-20 wt% of at least one polyolefin based elastomer.

In one aspect of the present invention, there is provided a process for producing a glass fiber reinforced thermoplastic composition.

The process for producing a glass fiber reinforced thermoplastic composition comprises the sequential steps of: i. unwinding from a package of at least one continuous glass multifilament strand; ii. applying from 0.5 to 20% by mass of an impregnating composition to said at least one continuous glass multifilament strand to form an impregnated continuous multifilament strand; and ill. applying a sheath of thermoplastic polymer around the impregnated continuous multifilament strand to form a sheathed continuous multifilament strand; in which, the impregnating composition comprises or consists of:

In one aspect of the present invention, there is provided a process for the preparation of an article.

The process for preparation of an article comprises the sequential steps of:

- Providing the thermoplastic composition of any of claims 1-13 or produced by the process of claim 14 in pellet form, and

- Injection molding the thermoplastic composition into an article.

Thermoplastic polymer

The thermoplastic composition of the present invention comprises a thermoplastic polymer matrix. The thermoplastic polymer matrix comprises at least one thermoplastic polymer.

Suitable examples of the thermoplastic polymer 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 terephthalate, polybutylene terephthalate; polycarbonates; polyphenylene ethers (PPE); polyphenylene sulphide (PPS); polyurethanes; also any type of polymer blends and compounds and any combinations thereon.

More particularly, polypropylene, polybutylene terephthalate and polyamide 6 may be used.

In some instances, the thermoplastic polymer is free of phthalates.

Polypropylene

In some instances, the thermoplastic polymer matrix of the present invention comprises at least one polypropylene polymer, which can be (al) a propylene homopolymer, (a2) a random copolymer of propylene and at least one other olefin, (a3) a propylene impact copolymer, (a4) a modified- or functionalized-propylene homopolymer or copolymer, or mixtures thereof.

The polypropylene is preferably crystallizable. The term "crystallizable" generally means that the polymer has an isotactic structure, i.e. its isotacticity is high, for instance higher than 95% and preferably higher than 98%.

A random copolymer generally contains at most about 20 mol % of other olefins as comonomer, preferably at most 10 mol %, to retain crystalline character. The at least one other olefin may be for instance an alpha-olefin, in particular a 1-alkene having for instance 2 or 4-20, preferably 4-12, carbon atoms or cyclic olefins, optionally containing more than one ring, having a double bond in the ring structure. Examples of suitable olefins include ethylene, butene, hexene, styrene, cyclopentene and norbornadiene. Preferably, the alpha-olefin is a 1-alkene having 2, 4, 6 or 8 carbon atoms, more preferably, the alpha-olefin is ethylene. Preferably, the polypropylene polymer is a propylene impact copolymer, because this results in a favorable combination of stiffness and toughness. Propylene impact copolymers are also referred to as propylene block-copolymers or as heterophasic polypropylene copolymers. Such material basically has at least a two-phase structure, consisting of a crystalline propylene-based matrix and a dispersed elastomeric phase, typically an ethylene-olefin copolymer like an ethylene-propylene rubber (EPR). These polypropylenes are generally prepared in one or more reactors, by polymerization of propylene in the presence of a catalyst, and subsequent polymerization of an ethylene-olefin copolymer like an ethylene-propylene rubber (EPR), but may also be prepared by blending individual components, as is well known to a skilled person. The resulting polymeric materials are heterophasic, but their specific morphology usually depends on the preparation method and monomer types and ratios. In some instances, the polyolefin should have least one crystalline melting point (Tm) between 120 and 170C wherein the Tm has a heat capacity (dHm) of at least 10 J/g. Tm and dHm are determined by DSC as per ASTM D3418 with a heating rate of 20C/min.

Generally, the impact copolymer contains about 50-95 mass % of a crystalline propylene homo- or random-copolymer matrix, and about 50-5 mass % of dispersed copolymer of ethylene and at least one other olefin.

The amount of dispersed phase is preferably 10-35 mass %, more preferably 15-30 or 17-25 mass % of the total amount of heterophasic polymer, to arrive at a desired stiffness-impact balance in the composition according to the invention.

The dispersed phase comprises a copolymer of ethylene and at least one other olefin, preferably a C3 to CIO alpha-olefin. Examples of suitable C3 to CIO alpha-olefins include 1-butene, 1-pentene, 4-methyl-l- pentene, 1-hexene, 1-heptene and 1-octene. Preferably, an ethylene-propylene copolymer, known also as ethylene-propylene rubber (EPR) is used as the dispersed phase.

The amounts of the propylene-based matrix and the dispersed ethylene-olefin copolymer may be determined by NMR, as well known in the art.

Preferably, the propylene-based matrix is a propylene homopolymer.

Preferably, the melt flow index (MFI) of the propylene-based matrix (MFIPP) is at least 30 dg/min and at most 120 dg/min, measured according to ISO1133 (2.16 kg/230°C). MFIPP may be for example at least 40 dg/min, at least 45 dg/min, at least 50 dg/min, at least 55 dg/min or at least 60 dg/min, and/or for example at most 110 dg/min, at most 100 dg/min, at most 90 dg/min or at most 80 dg/min, measured according to ISO1133 (2.16 kg/230°C).

The propylene-based matrix is preferably semi-crystalline, that is, it is not 100% amorphous, nor is it 100% crystalline. For example, the propylene-based matrix is at least 40% crystalline, for example at least 50%, for example at least 60% crystalline and/or for example at most 80% crystalline, for example at most 70% crystalline. For example, the propylene-based matrix has a crystallinity of 60 to 70%. For purpose of the present invention, the degree of crystallinity of the propylene-based matrix is measured using differential scanning calorimetry (DSC) according to ISO11357-1 and ISO11357-3 of 1997, using a scan rate of 10°C/min, a sample of 5mg and the second heating curve using as a theoretical standard for a 100% crystalline material 207.1 J/g.

The MFI of the dispersed ethylene-olefin copolymer (MFIEPR) may be for example at least 0.001 dg/min, at least 0.01 dg/min, at least 0.1 dg/min, at least 0.3 dg/min, at least 0.7 dg/min, at least 1 dg/min, and/or for example at most 30 dg/min, at most 20 dg/min, at most 15 dg/min, at most 10 dg/min, at most 5 dg/min, at most 3 dg/min, as measured according to ISO1133 (2.16 kg/230°C).

The amount of ethylene in the ethylene-olefin copolymer is preferably in the range from 20 to 80 wt% based on the ethylene-olefin copolymer, more preferably, the amount of ethylene in the ethylene-olefin copolymer is from 30 to 70 wt%, more preferably from 40 to 65 wt%, more preferably from 50 to 65 wt%, even more preferably from 55 to 65wt%.

Preferably, the a-olefin in the ethylene-a-olefin copolymer is propylene.

The MFI of the polypropylene polymer is in the range from 17 to 75 dg/min, preferably in the range from 20 to 60 dg/min, more preferably in the range from 25 to 55 dg/min, even more preferably in the range from 28 to 40 dg/min as measured according to ISO1133 (2.16 kg/230°C).

The xylene soluble part of the polypropylene polymer according to the invention is in the range from 9.3 to 19.6 wt%, preferably in the range from 11.2 to 18.4 wt%, more preferably in the range from 12.4 to 17.4 wt% as measured according to by 15016152:2005.

The intrinsic viscosity of the xylene soluble part of the polypropylene is preferably in the range from 1.2 to 4.6 dl/g, preferably in the range from 1.8 to 4.0 dl/g, even more preferably in the range from 2.3 to 3.5 dl/g as measured according to 1501628-1:2009 in decalin at 135 °C. Preferably, the polypropylene has a crystalline melting point (Tm) of between 120 and 170C, wherein the Tm has a heat capacity (dHm) of at least 10 J/g. Tm and dHm are determined by DSC as per ASTM D3418 with a heating rate of 20C/min. In some instances, the polyolefin will be free of phthalates.

The thermoplastic polymer matrix may also contain a modified polypropylene; this generally improves properties by affecting glass fibers-polypropylene interactions. Examples of suitable modified polypropylenes are polypropylenes grafted with for instance an unsaturated organic compound, like a carboxylic acid, an anhydride, an ester, glycidyl esters or salts thereof. Suitable examples include maleic, fumaric, (meth)acrylic, itaconic or cinnamic acid or anhydride, ester or carboxylic acid salt thereof. Preferably, maleic anhydride is used. The amount of modified polypropylene may vary widely, but for economic reasons the amount normally will be rather low, for instance less than 5 mass %, preferably less than 4, 3, 2 or even 1 mass % (based on total composition).

The polypropylene polymer according to present invention can be produced using any conventional technique known to the skilled person, for example multistage process polymerization, such as bulk polymerization, gas phase polymerization, slurry polymerization, solution polymerization or any combinations thereof. Any conventional catalyst systems, for example, Ziegler-Natta or metallocene may be used. Such techniques and catalysts are described, for example, in W006/010414;

Polypropylene and other Polyolefins, by Ser van der Ven, Studies in Polymer Science 7, Elsevier 1990; W006/010414; US4399054 and US4472524. Preferably, the polypropylene is made using Ziegler-Natta catalyst.

Polyolefin-based elastomer

In one aspect of the present invention, the thermoplastic composition in the present invention preferably further comprises a polyolefin-based elastomer.

The polyolefin-based elastomer is preferably selected from a group consisting of ethylene-l-butene copolymer, ethylene-l-hexene copolymer, ethylene-l-octene copolymer and mixtures thereof, more preferably, the elastomer is selected from ethylene-l-octene copolymer. Most preferably, the elastomer is an ethylene-l-octene copolymer.

Preferably the density of the polyolefin based elastomer is in the range from 0.845 to 0.883 g/cm3, preferably in the range from 0.848 to 0.865 g/cm3, more preferably in the range from 0.853 to 0.860 g/cm3 as measured according to ASTM D792-13. Preferably the MFI of the polyolefin based elastomer is in the range from 0.5 to 18.0, preferably in the range from 0.8 to 14.2 dg/min as measured according to ASTM D1238-13, 190°C, 2.16kg.

The shore A hardness of the polyolefin based elastomer is preferably in the range from 35 to 90, preferably in the range from 42 to 69, more preferably in the range from 47 to 60 as measured according to ASTM D2240-15, Is.

The inventors of the present invention surprisingly found that the thermoplastic composition according to the present invention comprising a polyolefin based elastomer having an MFI in the range from 0.8 to 14.2 dg/min as measured according to ASTM D1238-13,190°C, 2.16kg and a density in the range from 0.853 to 0.860 g/cm3 as measured according to ASTM D792-13 has an excellent falling weight impact resistance at -40°C.

The polyolefin-based elastomers which are suitable for use in the current invention are commercially available for example under the trademark EXACT™ available from Exxon Chemical Company of Houston, Texas, or under the trademark ENGAGE™ polymers, a line of metallocene catalyzed elastomers available from Dow Chemical Company of Midland, Michigan, or under the trademark TAFMER™ available from MITSUI Chemicals Group of Minato Tokyo, or under the trademark Fortify™ and Cohere™ available from SABIC.

The polyolefin-based elastomers may be prepared using methods known in the art, for example by using a single site catalyst, i.e., a catalyst the transition metal components of which is an organometallic compound and at least one ligand of which has a cyclopentadienyl anion structure through which such ligand bondingly coordinates to the transition metal cation. This type of catalyst is also known as "metallocene" catalyst. Metallocene catalysts are for example described in U.S. Patent Nos. 5,017,714 and 5,324,820. The elastomer s may also be prepared using traditional types of heterogeneous multisited Ziegler-Natta catalysts.

Preferably, the amount of ethylene incorporated into the polyolefin-based elastomer is at least 45 wt%. More preferably, the amount of ethylene incorporated into the polyolefin based elastomer is at least 48 wt%, for example at least 50 wt%. The amount of ethylene incorporated into the polyolefin based elastomer may typically be at most 95 wt%, for example at most 85 wt%, for example at most 75 wt%, for example at most 65 wt%, for example at most 60 wt%, for example at most 58 wt%. The amount of the polyolefin-based elastomer is preferably in the range from 5 to 20 wt%, more preferably in the range from 7 to 15 wt% based on the total amount of the thermoplastic composition.

Glass Fibers

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 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.

The thermoplastic composition comprises 10-70 mass % of glass fibers, preferably 5-25 mass %, and more preferably 5-20 mass %.

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 PP composition.

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.

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 wire-coating 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.

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 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.

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 10 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 compression 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 Bl and EP 0994978 Bl describe a typical sheathing or wire-coating method.

The average length of the glass fibers in the composition of the invention 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 is preferably at most 40 mm, more preferably at most 30, 20 or 15 mm. A composition containing fibers of average length 0.1-10 mm is found to present an optimum in mechanical properties, shrinkage and scratch-resistance of the molded article obtained thereof.

The diameter of the glass fibers in the composition according to the invention is not very critical, but very thick fibers may result in a decrease of mechanical properties and/or lower surface quality. Generally, the diameter ranges from 5 to 50 microns, preferably from 5 to 30 microns, more preferably from 8 to 25 microns.

The amount of glass fibers affects mechanical properties, as well as processing and mold shrinkage behavior, and aesthetic aspects of the molded article obtained thereof and, depending on the desired properties profile, the amount can be optimized.

Preferably, the glass fiber is an E-glass fiber known in the art possessing low electrical conductivity, for example a glass made from the oxides of silicon, aluminum, calcium, magnesium, and boron. Other well- known glass compositions such as high strength S-glass, chemically resistant C-glass or low dielectric constant D-glass may also be used.

The filament density of the continuous glass multifilament strand may vary within wide limits. Preferably, the continuous multifilament strand may have of from 500 to 10000 glass filaments/strand and more preferably from 2000 to 5000 glass filaments/strand, 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.

Impregnating agent

The thermoplastic composition of the present invention comprises an impregnating composition.

The amount of impregnating composition applied to the glass multifilament strand depends on the thermoplastic matrix, on the size (diameter) of the filaments forming the continuous strand, and on type of sizing that is on the surface of the fibers.

According to the present invention, the amount of impregnating composition applied to the continuous glass multifilament strand should be at least 0.5% by mass, preferably it is at least 2% by mass, more preferably at least 4% by mass and most preferably at least 6% by mass; but should be at most 20% by mass, preferably it is at most 18% by mass, more preferably at most 15% by mass and most preferably at most 12% by mass. A certain minimum amount of impregnating composition 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.

It is found that the lower the viscosity, the less impregnating composition can be applied. For instance, in case the thermoplastic polymer matrix is polypropylene homopolymer with a melt index MFI of 25 to 65 g/10 min (230°C/2.16 kg) and the reinforcing long glass filaments have a diameter of 19 micron, the impregnating composition is preferably applied to the multifilament strand in an amount of from 2 to 10% by mass.

The impregnating composition of the present invention comprises or consists of:

(cl) at least one impregnating agent, and

(c2) at least one EVA wax, in an amount of 5 to 99wt % of the total weight of the impregnating composition, preferably 10 to 50% of the impregnating composition and in other instances 15 to 40% of the impregnating composition . The at least one impregnating agent is used in an amount of l-95wt% of the total weight of the impregnating composition, preferably 50-90wt% of the total weight of the impregnating composition, and more preferably 60-85wt% of the total weight of the impregnating composition.

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 enhance dispersion of the glass fibers in the thermoplastic polymer matrix during the moulding process.

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.

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 160°C.

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 polypropylene having a melting point of about 160°C, the melting point of the impregnating agent may be at most about 140°C.

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 example, when the matrix is polypropylene, the application temperature of the impregnating agent can be from 15 to 200°C. 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. The skilled man can select suitable combinations based on general knowledge, and may also find such combinations in the art. Suitable examples of impregnating agents include low molar mass compounds, for example low molar mass or oligomeric polyurethanes, polyesters such as unsaturated polyesters, polycaprolactones, polyethyleneterephthalate, poly(alpha-olefins), such as highly branched polyethylenes and polypropylenes, polyamides, such as nylons, and other hydrocarbon resins. As a general rule, a polar thermoplastic polymer matrix requires the use of an impregnating agent containing polar functional groups; a non-polar polymer matrix involves using an impregnating agent having non-polar character, respectively. For example, for reinforcing a polyamide or polyester, the impregnating agent may comprise low molecular weight polyurethanes or polyesters, like a polycaprolactone. For reinforcing polypropylenes, the impregnating agent may comprise highly branched poly(alpha-olefins), such as polyethylene waxes, modified low molecular weight polypropylenes, mineral oils, such as, paraffin or silicon and any mixtures of these compounds. Preferably, the impregnating agent comprises a highly branched poly(alpha-olefin) and, more preferably, the impregnating agent is a highly branched polyethylene wax, in case the thermoplastic polymer to be reinforced is polypropylene; the wax optionally being mixed with for example from 10 to 80, preferably 20-70, mass% of a hydrocarbon oil or wax like a paraffin oil to reach the desired viscosity level.

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.

EVA wax

As one of the essential components, the impregnating composition comprises an EVA wax.

EVA wax is a copolymer of ethylene and vinyl acetate (VA). Due to the polar co-monomer VA, EVA waxes show, compared to PE waxes, a polar, more flexible, less brittle property. The polarity and flexibility can be adjusted by changing the proportion of VA in the EVA. In some instances, the EVA wax has a VA content in the range of 5 to 40 wt%, preferably 15 to 30 wt%, more preferably 18 to 28 wt%. A VA content above about 40 wt% may give too much moisture absorption and may show insufficient thermoplastic polymer matrix compatibility to be fully useful, while a VA content below 5% may not give enough wetout performance of the polar GF surface.

Vinyl acetate content may be determined by many techniques known in the art for example by infrared spectroscopy as per ASTM E168.

The EVA wax may also comprise C3 to C8 olefins or carboxylic acid functionality (acid terpolymers). All EVA (ethylene vinyl acetate) resins may be effective to some extent but best performance is achieved with a VA content of 10 to 25 wt% with a high melt flow (Melt Index) of 300 to 800 g/10 min at 190C, 2.16Kg for example as per ASTM D1238. EVA resins with 18 to 28% VA have the best polyolefin compatibility.

In some instances, the EVA wax has a melt flow Index (MFI) of 300 to 800 g/10 min at 190C, 2.16Kg as measured according to ISO 1133, preferably 400 to 600 g/10 min. A low melt flow EVA (<50 g/lOmin) may not have enough flow to quickly wetout the GF during the short (< 1 to 2 minute) injection molding and glass fiber coating processes.

Other additives

The thermoplastic composition of the present invention may further optionally comprise 0-20 mass % of other additives. This includes customary additives like nucleating agents, clarifiers, stabilizers, release agents, plasticizers, anti-oxidants, UV stabilizers like HALS compounds, colorants, flame-retardant additives, minerals, lubricants like calcium stearate, mold release agents, flow enhancers and/or antistatic agents. The skilled person will know how to select the type and amount of additives when needed, and to apply them in such amount that they do not detrimentally influence the aimed properties of the composition.

In order to further enhance especially scratch resistance, also anti-scratch additives like silicones may be added, as is know from other publications.

In an example of the present composition, it comprises one of more of the following additives:

0.05 to 5.0% of a nucleant such as talc, metal stearate or the like, 0.10 to 0.8% of a mold release such as fatty acid esters e.g. PETS (pentaerythritol tetra stearate) or GMS (glycerol mono stearate), fatty acid amides e.g. EBS wax, polyolefins and the like,

0.1 to 1.0% of antioxidants such as hindered phenols, phosphorus containing stabilizers, thioesters, lactones or combinations thereof,

0.1 to 5% of colorants such as carbon black and zinc sulfide, and in some instances less than 100 ppm titanium dioxide that may break glass fiber reducing fiber length and impair mechanical property performance.

In some instances, the composition may further comprise glass-resin coupling agents such as alkoxy silanes, amino silanes, zirconates, titanates, and maleic anhydride (MA) or glycidyl methacrylate (GMA) modified polyolefins such as PEgGMA, PPgMA, to improve GF resin adhesion.

Method of production

The composition according to the invention can be made with known processes, for example by mixing all components, except for the glass fiber, on an extruder, to obtain the composition of pellet or granule form. The composition can also be made by blending different pellets of different compositions. Preferably, the composition is a mixture of pellets of different compositions, and contains a masterbatch (or concentrate) of glass fibers; that is a composition based on a polypropylene polymer and 30-75 mass % of long glass fibers. The polypropylene in this masterbatch is as above described for polypropylene according to the invention, and may be the same as or different from the polypropylene in other pellets. The advantage hereof is that the LGF PP compound can be made in an efficient way, and the total amount of glass fibers in the final composition, and in the further molded article, can be easily adjusted to optimize performance. Preferably, the masterbatch contains 35-70, 40-65, or 45-60 mass % of glass fibers.

The molded article according to the invention can be a semi-finished or finished article made from the polypropylene composition by a molding process. Examples of suitable molding processes include injection molding, compression molding, extrusion and extrusion compression molding. Injection molding is most widely used to produce articles such as automotive parts. A semi-finished article may subsequently undergo further known processing steps. The article according to the invention preferably has a so-called textured surface, which further reduces sensitivity to and/or visibility of surface damage like scratches. Generally, the length of glass fibers in a polymer composition decreases during a melt processing step like injection molding. The average length of the glass fibers in the molded article made from the composition according to the invention may vary widely, depending on both starting length and processing conditions. Preferably, the average fiber length in the molded article is at least 0.5, 0.6, 0.7, 0.8 or 0.9 mm, and most preferably between about 1 and 5 mm.

The invention further relates to the use of a molded article according to the invention in applications wherein in addition to e.g. good tensile and impact properties also aesthetic aspects are important, such as visible (non-painted) parts for automotive exterior and interior applications, or electrical appliances. Examples of automotive parts include bumper beams, bumper fascia, instrument panel structures, pillars, consoles, interior trim parts, and door panel parts.

LGF articles of the invention may be made by injection molding, gas assist molding, compression molding, foam molding, profile extrusion or any combination thereof. Article wall thickness will be from 0.1 to 10 mm. Automotive parts for example, can comprise battery trays, side rails, battery caps, spoilers, door panels, bumpers, brackets, supports and the like. The LGF articles may further comprise metallic stiffeners and supports, connectors or metal fastening devices.

The present invention further relates to a process for the preparation of the article comprising the following sequential steps:

- Providing the polymer composition according to the invention in pellet form.

- Injection molding the polymer composition into an article.

The present invention further relates to the use of the polymer composition according to the invention in an article, preferably the article is an automotive part.

Experimental Examples

Several long glass fiber reinforced polypropylene compositions were prepared in the form of pellets in accordance with the method disclosed in EP 2,219,839.

Continuous glass fiber multifilament strands were unwound from the packages and transported to the impregnating agent applicator. The impregnating agent was molten and mixed at a temperature of 160°C and applied to the continuous glass multifilament strand. The sheathing step was performed in-line directly after the impregnating step, using a 75 mm twin screw extruder (manufactured by Berstorff, screw UD ratio of 34), at a temperature of about 250° C, which fed the molten polypropylene matrix material and additives to an extruder-head wire-coating die. The sheathed strand was cut into pellets of 15 mm length. The pellets having a fiber glass core surround by a wax mixture encased by the polypropylene (PP) were moulded into appropriate shapes for the measurements of various properties as given in Table 2.

The components used to prepare the compositions are as follows:

SABIC® PP 595A is a polypropylene homopolymer commercially available from SABIC with a melt flow rate of 47 dg/min, tested in accordance with ISO 1133 at 230C and 2.16kg, and a density of 905 kg/m3, tested in accordance with ASTM D1505 at 23C. It has a melting point of 162C with a heat of melting (dHm) above 30J/g.

Tufrov 9000 is a continuous E glass roving provided by NEG (Nippon Electric Glass). The fiber glass coating comprises a functionalized silane coupling agent.

Dicera 13082 PARAMELT is a polyethylene wax, which is a mixture of polyolefin components and is described in EP 2,219,839.

Elvax® 410 is an ethylene vinyl acetate (EVA) copolymer with 18wt% vinyl acetate comonomer content, commercially available from DuPont, with a melt flow rate of 500 g/10 min (190C, 2.16 Kg, as per ASTM D1238).

AO B225 is an antioxidant mixture of a hindered phenol (IRGANOX 1076) and a triaryl phosphite (IRGAFOS 168) from BASF Co.

UV 119 is a high molecular weight hindered light amine stabilizer (HALS), SABOSTAB UV119 from Sabo Co.

CA PO1020 is a maleic anhydride functionalized polypropylene copolymer available as EXXELOR PO1020 from EXXON-MOBIL.

CMB is a polypropylene carbon black masterbatch with 25% carbon black.

Table 1. Components and respective amounts of the compositions, in wt%.

As shown in table 1, comparative example 1 (CE1) comprises 53.44wt% of polypropylene, 40.2wt% of long glass fiber as reinforcement, 4.0wt% of a polyethylene wax, and several functional additives.

Example 1 (El) replaces 0.6wt% of the polyethylene wax with an EVA wax based on the composition of CE1, serving as a "15% EVA" example. Examples 2 and 3, respectively, replaces 1.0wt% and 1.6wt% of the polyethylene wax with an EVA wax, as a "25% EVA" and "40% EVA" example.

The compositions were then injection molded into appropriate shapes, aged at 23C and 50% RH for 7 days after molding, and tested under standard conditions, as reported in table 2.

Table 2. Ash content, Charpy impact resistance, Flexural and Tensile modulus of the compositions.

Fig. 1 plots Charpy impact resistance against EVA content of the examples.

Fig. 2 plots Flexural strength against EVA content of the examples.

Fig. 3 plots Tensile strength against EVA content of the examples. As can be clearly seen from table 2 and figs. 1-3, with added EVA (Ex 1- 3), Charpy impact is improved by 37 to 46% over the comparative example. Flexural strength is improved by 27 to 34% while tensile strength is increases by 23 to 24%.

These significant improvements impart LGF PP articles with better crash strength in large automotive parts for example battery trays and side rails as well as bumpers. Also, melt flow and processability are retained, as is the appearance of the parts (similar color, gloss and surface uniformity).

Claims

1. A glass fiber-reinforced thermoplastic composition comprising, based on a total weight thereof:

(a) 30-90 wt% of a thermoplastic polymer matrix,

(b) 10-70 wt% of glass fibers, and

(c) 0.5-20 wt% of an impregnating composition comprising or consisting of:

2. The thermoplastic composition of claim 1, further comprising:

(d) 5-20 wt% of at least one polyolefin based elastomer.

3. The thermoplastic composition of any of the preceding claims, wherein the thermoplastic polymer matrix comprises at least one polypropylene polymer.

4. The thermoplastic composition of any of the preceding claims, wherein the polypropylene polymer is polypropylene homopolymer.

5. The thermoplastic composition of any of the preceding claims, wherein the (cl) at least one impregnating agent comprises a highly branched poly(alpha-olefin).

6. The thermoplastic composition of claim 5, wherein the highly branched poly(alpha-olefin) is a polyethylene wax.

7. The thermoplastic composition of any of the preceding claims, wherein the amount of the impregnating composition is 2-10 wt%.

8. The thermoplastic composition of any of the preceding claims, wherein the amount of the (c2) at least one EVA (ethylene vinyl acetate) wax is 10-50 wt% of the impregnating composition, preferably 15-

9. The thermoplastic composition of any of the preceding claims, wherein the (c2) at least one EVA (ethylene vinyl acetate) wax has a melt flow index in the range of 300 to 800 g/10 min at 190C and 2.16Kg as per ASTM D1238.

10. The thermoplastic composition of any of the preceding claims, wherein the (c2) at least one EVA wax has a VA (vinyl acetate) content of 5-40 wt%, preferably 15-30 wt%, more preferably 18-28wt%.

11. The thermoplastic composition of claim 3, wherein the polypropylene polymer has at least one property selected from:

• an MFI, as measured according to ISO 1133 at 230°C/2.16kg, in the range of 17-75 dg/min, preferably 20-60 dg/min, more preferably 25-55 dg/min, even more preferably 28-40 dg/min,

• a xylene soluble part, as measured according to ISO 16152:2005, in the range of 9.3-19.6 wt%, preferably 11.2-18.4 wt%, more preferably 12.4-17.4 wt%,

• an intrinsic viscosity of the xylene soluble part, as measured according to ISO 1628-1:2009 in decalin at 135 °C, in the range of 1.2-4.6 dl/g, preferably 1.8-4.0 dl/g, more preferably 2.3-3.5 dl/g.

12. The thermoplastic composition of claim 2, wherein the polyolefin based elastomer has at least one property selected from:

• a shore A hardness, as measured according to ASTM D2240-15, Is, in the range of 35-90, preferably 42-69, more preferably 47-60,

• a density, as measured according to ASTM D792-13, in the range of 0.845-0.883 g/cm3, preferably 0.848-0.865 g/cm3, more preferably 0.853-0.860 g/cm3.

13. The thermoplastic composition of claim 2, wherein the polyolefin based elastomer is an ethylene-1- octene copolymer.

14. A process for producing a glass fiber reinforced thermoplastic composition, which comprises the sequential steps of: i. unwinding from a package of at least one continuous glass multifilament strand; ii. applying from 0.5 to 20% by mass of an impregnating composition to said at least one continuous glass multifilament strand to form an impregnated continuous multifilament strand; and iii. applying a sheath of thermoplastic polymer around the impregnated continuous multifilament strand to form a sheathed continuous multifilament strand;

Characterized in that the impregnating composition comprises or consists of:

15. Process for the preparation of an article comprising the sequential steps of: - Providing the thermoplastic composition of any of claims 1-13 or produced by the process of claim 14 in pellet form, and

- Injection molding the thermoplastic composition into an article.