Translucent polypropylene-based material for additive manufacturing

Abstract

Provided is a filament for 3D printing comprising a polyolefin composition (I) comprising: (A) 55-85 wt% of a copolymer of propylene with ethylene and / or a C4-C10 alpha-olefin having MFR(A) of 5.0-50 g / 10min; (B) 10-30% by weight of a styrene or alpha-methylstyrene block copolymer; (C) 1-20% by weight of glass fibers; and (D) 0-2% by weight of a compatibilizer, wherein the amounts of components (A), (B), (C) and (D) are based on the total weight of the polyolefin composition (I), and a 3D printing method making use of said filament.

Description

TITLETRANSLUCENT POLYPROPYLENE-BASED MATERIAL FOR ADDITIVE MANUFACTURINGFIELD OF THE INVENTION

[0001] The present disclosure relates to the field of additive manufacturing, in particular to the use of a glass-fiber filled polypropylene composition for 3D printing and to a 3D printing filament comprising said composition.BACKGROUND OF THE INVENTION

[0002] In recent years, 3D printing technology has revolutionized the manufacturing landscape by providing a versatile and efficient means of creating three-dimensional objects layer by layer. Various materials have been employed in the 3D printing process, each offering unique properties and applications. This patent focuses on a novel approach to 3D printing utilizing polypropylene- based materials, with an emphasis on achieving good mechanical and optical properties, in combination with enhanced adhesion between successive layers during the printing process.

[0003] Polypropylene-based 3D printing materials are known in the art. The international patent application WO2018 / 069025 discloses filaments for 3D printing comprising an heterophasic polypropylene composition with a xylene soluble content of 15-50 wt.% and MFR of 0.5-100 g / lOmin.

[0004] More complex polypropylene-based compositions for additive manufacturing containing an heterophasic propylene polymer in combination with 2-15 wt.% of an elastomeric block copolymer comprising styrene and 5-50 wt.% of glass fibers are disclosed in the international patent application WO2021 / 069242. Said polypropylene-based compositions are characterized by low warpage when used in an extrusion based 3D printing process.

[0005] Warpage occurs due to material shrinkage while 3D printing, which causes the corners of the print to lift and detach from the build plate. When plastics are printed, they firstly expand slightly but contract as they cool down. If material contracts too much, this causes the print to bend up from the build plate and deformed 3D printed objects are obtained.

[0006] Filaments for 3D printing with reduced warpage made from propylene / ethylene copolymers or propylene / ethylene / butene-1 terpolymers are known from the patent applications WO2017 / 182209 and WO2017 / 182211 respectively.

[0007] The above mentioned patent applications are silent about the optical properties of the 3D printed objects. 3D printed materials for light coverings having good optical properties are generally made by polycarbonate or PLA, but suffer from limited mechanical properties profile.

[0008] It has been surprisingly found that polypropylene compounds containing a propylene copolymer or terpolymer, in combination with a styrenic block copolymer and glass fibers can be conveniently used in additive manufacturing to obtain 3D printed objects having good optical properties, a good balance of mechanical properties, low warpage and shrinkage and good layer adhesion.SUMMARY OF THE INVENTION

[0009] In a first aspect, the present disclosure provides a filament for extrusion-based additive manufacturing comprising a polyolefin composition (I) comprising:

[0010] (A) from 55 to 85% by weight of a copolymer of propylene with ethylene and / or a C4-C10 alpha-olefin having a melt flow rate MFR(A) of from 5.0 to 50 g / lOmin (ISO 1133-1 :2011; 230°C / 2.16 kg);

[0011] (B) from 10 to 30% by weight of a styrene or alpha-methylstyrene block copolymer;

[0012] (C) from 1.0 to 20% by weight of glass fibers; and

[0013] (D) from 0 to 2.0% by weight of a compatibilizer,

[0014] wherein the amounts of components (A), (B), (C) and (D) are based on the total weight of the polyolefin composition (I).

[0015] In a second aspect, the present disclosure provides a process to make the filament of the first aspect, the process comprising the steps of:

[0016] (a) providing the polyolefin composition (I) or the components from (A) to (D), and optionally (E);

[0017] (b) extruding the polyolefin composition (I) or the components from (A) to (D), and optionally (E) through a die, thereby obtaining a filament; and

[0018] (c) cooling the filament, and optionally rolling up the filament on a coil.

[0019] In a third aspect, the present disclosure provides a 3D printing method comprising the steps of:

[0020] (i) providing a filament according to the first embodiment;

[0021] (ii) configuring a 3D printer with an extruder assembly, a heated extruder nozzle and a build platform;

[0022] (iii) extruding the filament through the heated extruder nozzle in a controlled manner, thereby building successive printed layers of the desired object on the build platform based on a digital 3D model;

[0023] (iv) allowing each printed layer to cool and solidify before proceeding to the next layer.

[0024] In a fourth aspect, the present disclosure refers to a 3D printed object obtained by the 3D printing method of the third aspect.

[0025] While multiple embodiments are disclosed, still other embodiments will become apparent to those skilled in the art from the following detailed description. As will be apparent, certain embodiments, as disclosed herein, are capable of modifications in various obvious aspects, all without departing from the spirit and scope of the claims as presented herein. Accordingly, the following detailed description is to be regarded as illustrative in nature and not restrictive.BRIEF DESCRIPRION OF THE DRAWINGS

[0026] FIG.1 provides a schematic representation of the 3D printed frame used to determine warpage.

[0027] FIG.2 provides a lateral view of the schematic representation of the 3D printed frame used to determine % warpage.

[0028] Figures from FIG.3A to FIG.3C provides a schematic representation of the infill orientation of 3D printed specimens of Examples E1-E3 and E5-E7 and Comparative Examples CE4, CE8 and CE9, wherein:

[0029] - FIG.3A illustrates the infill orientation for 0° test specimens;

[0030] - FIG.3B illustrates the infill orientation for the 45° test specimens; the infill orientation of adjacent layers is mutually perpendicular, i.e. the first layer is printed at +45° and the adjacent at -45°; and

[0031] - Fig.3C illustrates the infill orientation for the z test specimens.DETAILED DESCRIPTION OF THE INVENTION

[0032] In the context of the present disclosure;

[0033] - the percentages are expressed by weight, unless otherwise specified;

[0034] - the total weight of a polymer composition sums up to 100% by weight, unless otherwise specified;

[0035] - the term “comprising” referred to a polymer or to a polymer composition, mixture or blend should be construed to mean “comprising or consisting essentially of’;

[0036] - the term “consisting essentially of’ means that, in addition to those components which are mandatory, other components may also be present in the material, provided that the essential characteristics of the material are not materially affected by their presence. Examples of components that, when present in customary amounts, do not materially affect the characteristics of a polymer or of a polyolefin composition, mixture or blend are catalyst residues, antistatic agents and processing aids;

[0037] - the expressions “additive manufacturing” and “3D printing” are synonyms;

[0038] - the term “copolymer” refers to a polymer obtained by the intentional copolymerization of at least two different monomers, i.e. the term copolymer includes terpolymers.

[0039] In a first aspect, the present disclosure provides a filament for extrusion-based additive manufacturing comprising a polyolefin composition (I) comprising:

[0040] (A) from 55 to 85% by weight, preferably from 60 to 80% by weight, a copolymer of propylene with ethylene and / or a C4-C10 alpha-olefin having a melt flow rate MFR(A) of from 5.0 to 50 g / lOmin (ISO 1133-1:2011; 230°C / 2.16 kg);

[0041] (B) from 10 to 30% by weight, preferably from 17 to 27% by weight, of a styrene or alpha-methylstyrene block copolymer;

[0042] (C) from 1.0 to 20% by weight, preferably from 2.0 to 17% by weight, of glass fibers; and

[0043] (D) from 0 to 2.0% by weight, preferably from 0.1 to 1.5% by weight, of a compatibilizer,

[0044] wherein the amounts of components (A), (B), (C) and (D) are based on the total weight of the polyolefin composition (I).

[0045] In one embodiment, the filament consists of the polyolefin composition (I).

[0046] The individual components from (A) to (D) of the polyolefin compositions (I) are defined in greater detail below. The individual components may be comprised in the polyolefin composition (I) in any combination and with any degree of preference.

[0047] Preferably the alpha-olefin comprised in the propylene copolymer (A) is selected from butene- 1 and hexene- 1.

[0048] The component (A) is preferably selected from:

[0049] (Al) a propylene / ethylene copolymer having:

[0050] - an ethylene content of up to and including 4.0% by weight, preferably from 0.1 to4.0% by weight, more preferably from 0.5 to 3.5% by weight, based on the weight of the propylene / ethylene copolymer; and

[0051] - a solubility in xylene at 25°C equal to or lower than 10% by weight, preferably ranging from 0.1 to 10% by weight, more preferably from 1.0 to 8.0% by weight, based on the weight of the propylene / ethylene copolymer;

[0052] (A2) a propylene / ethylene / butene-1 terpolymer having:

[0053] - a content of units deriving from ethylene of from 0.5 to 2.0% by weight, preferably from 0.7 to 1.8% by weight, more preferably from 0.9 to 1.5% by weight, and a content of units derived from butene- 1 of from 3.5 to 7.0% by weigh, preferably from 4.0 to 6.5% by weigh, more preferably from 4.5 to 6.0% by weight, based on the weight of the propylene / ethylene / butene-1 terpolymer; and

[0054] - a solubility in xylene at 25°C equal to or lower than 7.0% by weight, preferably from2.0 to 7.0% by weight, more preferably from 3.0 to 6.0% by weight, based on the weight of the propylene / ethylene / butene-1 terpolymer; and

[0055] (A3) combinations thereof.

[0056] Preferably, the a propylene / ethylene / butene-1 terpolymer (A2) has at least one of the following properties, preferably all:

[0057] - a total comonomer content of from 4.2 to 7.5% by weight, based on the weight of the propylene / ethylene / butene-1 terpolymer; and / or

[0058] - a weight ratio ethylene to butene (C2 / C4) ranging from 0.12 to 0.20; and / or

[0059] - a melting temperature equal to or higher than 140°C, preferably ranging from 140°C to 152°C (ISO 11357-3:2018).

[0060] In an alternative embodiment, the propylene copolymer (A) is a propylene / ethy lene / hexene- 1 terpolymer.

[0061] The component (A) preferably has at least one of the following properties, more preferably all:

[0062] - tensile modulus (ISO 527-1,-2:2019) greater than 1000 MPa, more preferably in the range of from 1100 to 1400 MPa; and / or

[0063] - elongation at yield (ISO 527-1,-2:2019) in the range of from 10 to 20%; and / or

[0064] - Charpy impact strength (ISO 179:2010, 23°C, Type 1, Notch A) in the range of from4 to 10 kJ / m2; and / or

[0065] - heat deflection temperature B (HDT B) 0.45 MPa, unannealed, ISO 75B-l,-2) in the range of from 72 to 80°C.

[0066] The copolymers and terpolymers for use as component (A) are available on the market, like under the trademarks Moplen marketed by LyondellBasell, and can be prepared by polymerizing the relevant monomers in the presence of a highly stereospecific Ziegler-Natta catalyst system comprising the reaction product of:

[0067] i) a solid catalyst component comprising Ti, Mg, Cl, and at least an internal electron donor compound;

[0068] ii) an alkylaluminum compound and,

[0069] iii) an external electron-donor compound.

[0070] The solid catalyst component (1) preferably comprises TiCh in an amount securing the presence of from 0.5 to 10% by weight of Ti with respect to the total weight of the solid catalyst component (1).

[0071] The solid catalyst component (1) comprises at least one stereoregulating internal electron donor compound selected from mono or bidentate organic Lewis bases, preferably selected from esters, ketones, amines, amides, carbamates, carbonates, ethers, nitriles, alkoxysilanes and combinations thereof.

[0072] Preferred donors are the esters of phthalic acids such as those described in EP45977A2 and EP395083 A2, in particular di-isobutyl phthalate, di-n- butyl phthalate, di-n-octyl phthalate, diphenyl phthalate, benzylbutyl phthalate and combinations thereof.

[0073] Esters of aliphatic acids can also be selected from esters of malonic acids such as those described in WO98 / 056830, WO98 / 056833, WO98 / 056834, esters of glutaric acids such as those disclosed in WO00 / 55215, and esters of succinic acids such as those disclosed WOOO / 63261.

[0074] Particular type of diesters are those deriving from esterification of aliphatic or aromatic diols such as those described in W02010 / 078494 and USP 7,388,061.

[0075] In some embodiments, the internal donor is selected from 1,3-diethers such as those described in EP361493, EP728769 and WO02 / 100904.

[0076] Specific mixtures of internal donors, in particular of aliphatic or aromatic mono or dicarboxylic acid esters and 1,3-diethers as disclosed in W007 / 57160 and WO2011 / 061134 can be used as internal donor.

[0077] Preferred magnesium halide support is magnesium dihalide.

[0078] The amount of internal donor that remains fixed on the solid catalyst component (1) is 5 to 20% by moles, with respect to the magnesium dihalide.

[0079] Preferred methods for the preparation of the solid catalyst component (1) are described in EP395083 A2.

[0080] The preparation of catalyst components according to a general method is described for example in European Patent Applications US4,399,054, US4,469,648, W098 / 44009A1 and EP395083A2.

[0081] In some embodiments, the catalyst system comprises an Al-containing cocatalyst (2) selected from Al-trialkyls, preferably selected from the group consisting of Al-triethyl, Al- triisobutyl and Al-tri-n-butyl. The Al / Ti weight ratio in the catalyst system is from 1 to 1000, preferably from 20 to 800.

[0082] In embodiments, the catalyst system comprises a further electron donor compound (3) (external electron donor) selected among silicon compounds, ethers, esters, amines, heterocyclic compounds, particularly 2,2,6,6-tetramethylpiperidine, and ketones.

[0083] Preferred silicon compounds are selected among methylcyclohexyldimethoxysilane (C-donor), dicyclopentyldimethoxysilane (D-donor) and mixtures thereof.

[0084] The component (A) is preferably but not exclusively prepared with a polymerization process and in a polymerization reactor illustrated in the European patent EP1012195B1. This polymerization process is carried out in a gas-phase reactor, called multizone circulating reactor (MZCR), having two interconnected polymerization zones. The polymer particles flow upwards through a first polymerization zone, denominated “riser”, under fast fluidization or transport conditions, leave said riser and enter a second polymerization zone, denominated “downcomer”, through which they flow in a densified form under the action of gravity. A continuous circulation of polymer is established between the riser and the downcomer. Generally, a condition of fast fluidization is established in the riser by feeding a gas mixture comprising the relevant monomers to the riser. The catalyst system is preferably fed to the reactor at any point of the riser.

[0085] In a multizone circulating reactor is optionally possible to obtain two polymerization zones with different composition by feeding a gas / liquid stream (barrier stream) to the upper part of the downcomer. The gas / liquid stream acts as a barrier to the gas phase coming from the riser, and is capable to establish a net gas flow upward in the upper portion of the downcomer. The established flow of gas upward has the effect of preventing the gas mixture present in the riser from entering the downcomer.

[0086] The molecular weight of the propylene copolymers is regulated using chain transfer agents, such as hydrogen or ZnEt2.

[0087] A multizone circulating reactor is preferably operated at a temperature of 50-120°C, more preferably of 70°-90°C, and at pressures of 0.5-10 MPa, more preferably of 1.5-6 MPa.

[0088] Alternatively, the component (A) is preferably prepared by polymerizing the relevant monomers in at least two polymerization stages, wherein the second and each subsequent polymerization stage is carried out in the presence of the polymer produced and the catalyst used in the immediately preceding polymerization stage. The polymerization can be carried out in continuous or in batch, either in liquid phase or in gas phase.

[0089] The liquid-phase polymerization can be either in slurry, solution or bulk (liquid monomer). This latter technology is the most preferred and can be carried out in various types of reactors such as continuous stirred tank reactors, loop reactors or plug-flow reactors.

[0090] The gas-phase polymerization can be carried out in fluidized or stirred, fixed bed reactors or in a multizone circulating reactor as illustrated in EPl 012195.

[0091] The reaction temperature is preferably comprised in the range from 40°C to 90°C and the polymerization pressure is from 3.3 to 4.3 MPa for a process in liquid phase and from 0.5 to 3.0 MPa for a process in the gas phase.

[0092] If needed, the polymer obtained at the end of the polymerization reaction can be optionally subject to a chemical treatment with organic peroxides in order to lower the average molecular weight and to increase the melt flow rate up to the value needed for specific applications.

[0093] The component (B) is a saturated or unsaturated styrene or alpha-methylstyrene block copolymer preferably a styrene block copolymer comprising up to and including 40% by weight of polystyrene, preferably from 10% to 35% by weight, more preferably from 15% to 30% by weight, based on the weight of the styrene block copolymer.

[0094] Preferably, the component (B) is a styrene block copolymer selected from the group consisting of: polystyrene-polybutadiene-polystyrene (SBS), polystyrene-poly(ethylene- butylenej-polystyrene (SEBS), polystyrene-poly(ethylene-propylene)-polystyrene (SEPS), polystyrene-polyisoprene-polystyrene (SIS), polystyrene-poly(isoprene-butadiene)-polystyrene (SIBS) and mixtures thereof; more preferably the styrene block copolymer is a polystyrene- poly(ethylene-butylene)-polystyrene (SEBS).

[0095] The styrene block copolymer (B) preferably has at least one of the following properties, preferably all:

[0096] - a melt flow rate MFR(B) measured according to ASTM D1238 (230°C, 2.16 Kg) ranging from 5 to 80 g / 10min., preferably from 10 to 60 g / 10min., more preferably from 10 to 30 g / 10 min; and / or

[0097] - a Shore A value measured according to ASTM 2240 (30 sec.) equal to or lower than70, preferably ranging from 30 to 70, more preferably from 30 to 60.

[0098] Styrene or alpha-methylstyrene block copolymers are prepared by ionic polymerization of the relevant monomers and are commercially available under the tradename of Kraton™ marketed by Kraton Polymers.

[0099] The component (C) is glass fibers preferably having diameter ranging from 5 to 20 microns, preferably from 8 to 15 microns; and length equal to or lower than 10 mm, preferably ranging from 0.1 to 10 mm, more preferably from 1 to 8 mm, more preferably from 2 to 7 mm, still more preferably from 3 to 6 mm.

[0100] Glass fibers suitable for use as component (C) are of the type known in the art suitable for compounding with polyolefin materials.

[0101] The compatibilizer (D) is optionally but preferably comprised in the polyolefin composition to increase the compatibility of the glass fibers with the components (A) and (B). The compatibilizer (D) is preferably a modified olefin polymer functionalized with polar compounds and, optionally, with a low molecular weight compound having a reactive polar group. Preferably, the modified olefin polymer is selected from polyethylenes, polypropylenes and combinations thereof.

[0102] The modified olefin polymers are selected from graft copolymers, block copolymers and combinations thereof.

[0103] Preferably, the modified polymers are functionalized with groups derived from polar compounds, including but not limited to acid anhydrides, carboxylic acids, carboxylic acid derivatives, primary and secondary amines, hydroxyl compounds, oxazoline, epoxides, ionic compounds and combinations thereof. Specific examples of said polar compounds are unsaturated cyclic anhydrides, their aliphatic diesters, and diacid derivatives.

[0104] Preferably, the compatibilizer (D) is a polyolefin, preferably selected from polyethylenes, polypropylenes and combinations thereof, functionalized with a compound selected from the group consisting of maleic anhydride, C1-C10 linear or branched dialkyl maleates, Cl- C10 linear or branched dialkyl fumarates, itaconic anhydride, Cl -CIO linear or branched itaconic acid dialkyl esters, maleic acid, fumaric acid, itaconic acid and mixtures thereof.

[0105] In a preferred embodiment, the compatibilizer (D) is a polyethylene and / or a polypropylene grafted with maleic anhydride (MAH-g-PP and / or MAH-g-PE).

[0106] Preferably, the compatibilizer (D) is a polyethylene and / or a polypropylene grafted with maleic anhydride, having at least one of the following properties, preferably all:

[0107] - a maleic anhydride graft level equal to or greater than 0.5 wt.%, based on the component (B), more preferably of from 0.5 wt.% to 3.0 wt.%, still more preferably from 0.75% to 2.0%; and / or

[0108] - a melt flow rate determined according to the method ISO 1133 (190°C, 2.16kg) ranging from equal to or greater than 80 g / 10min., preferably ranging from 80 to 200 g / lOmin.

[0109] Compatibilizers as described above are known in the art, and can be produced by functionalization processes carried out in solution, in the solid state or preferably in the molten state, eg. by reactive extrusion of the polymer in the presence of the grafting compound and of a free radical initiator. Functionalization of polypropylene and / or polyethylene with maleic anhydride is described for instance in EP0572028A1.

[0110] Examples of modified polyolefins suitable for use as compatibilizer are the commercial products Amplify™ TY by The Dow Chemical Company, Exxelor™ by ExxonMobil Chemical Company, Scona® TPPP by Byk (Altana Group), Bondyram® by Polyram Group and Polybond® by Chemtura and combinations thereof.

[0111] In a preferred embodiment, the polyolefin composition (I) further comprises up to and including 5.0% by weight, preferably from 0.01 to 3.0% by weight, based on the total weight of the polyolefin composition (I), of a component (E) being an additive of the type known in the art for use in polyolefin compositions, wherein the additive is more preferably selected from the group consisting of antistatic agents, antioxidants, light stabilizers, slipping agents, anti-acids, melt stabilizers, clarifiers, nucleating agents, pigments and combinations thereof. The polyolefin composition (I) comprising a nucleating agent and / or a clarifying agent results in 3D printed objects with lower light absorbance.

[0112] The component (E) is preferably metered to the polyolefin composition (I) as concentrated pre-mix, like dispersed in a polymeric carrier, preferably a propylene homopolymer.

[0113] The polyolefin composition (I) is preferably but not necessarily prepared by blending the component in a mixing apparatus wherein the polymeric components are at least partially melt, like an extruder. After extrusion, the polyolefin compositions (I) can optionally be pelletized.

[0114] The filament of the present disclosure preferably has diameter from 1.00 to 4.00 mm, preferably from 1.50 to 3.00 mm. In one embodiment the filament has diameter of 1.75 mm; in an alternative embodiment the filament has diameter of 2.85 mm.

[0115] The filament of the present disclosure is preferably prepared by a process comprising the steps of:

[0116] (a) providing the polyolefin composition (I) as described above or the components from(A) to (D), and optionally (E);

[0117] (b) extruding the polyolefin composition (I) or the components from (A) to (D), and optionally (E) through a die, thereby obtaining a filament; and

[0118] (c) cooling the filament, and optionally but preferably rolling up the filament on a spool.

[0119] Accordingly, in a second aspect the present disclosure provides a process to prepare the filament of the first aspect comprising the steps from (a) to (c) as described above.

[0120] The die of step (b) is preferably a round die.

[0121] In a further aspect, the present disclosure provides the use of the polyolefin composition (I) as described above in an extrusion-based additive manufacturing process.

[0122] The polyolefin composition (I) can be fed to a 3D printing device in the form of pellets or, preferably, as a filament according to the first aspect of the present disclosure.

[0123] Accordingly, the present disclosure also refers to the use of the filament of the first aspect in an extrusion-based additive manufacturing process.

[0124] In a further aspect, the present disclosure provides a 3D printing method comprising selectively depositing a layer of the polyolefin composition (I) as described above onto a substrate, like a build platform or a 3D printed layer of the polyolefin composition (I).

[0125] In a third aspect, the present disclosure provides a method for 3D printing comprising the steps of:

[0126] (i) providing a filament according to the first aspect of the present disclosure;

[0127] (ii) configuring a 3D printer with an extruder assembly, a heated extruder nozzle and optionally, but preferably, a build platform;

[0128] (iii) extruding the filament through the heated extruder nozzle in a controlled manner, thereby building successive printed layers of the desired object based on a digital 3D model;

[0129] (iv) allowing each printed layer to cool and solidify before proceeding to the next layer.

[0130] Preferably in step (ii) the extruder nozzle is heated to a predetermined temperature suitable for melting the filament and, optionally, by heating the build platform to enhance adhesion. Step (ii) preferably further comprises positioning the filament spool in the filament holder of the 3D printer.

[0131] Preferably, step (iii) comprises building successive printed layers of the desired object on the build platform. Optionally, step (iii) further comprises dynamically adjusting printingparameters, including layer height, print speed, and nozzle temperature, based on the specific requirements of the 3D model.

[0132] Optionally but preferably, the method further comprises a step (v) of removing the build platform from the 3D printed object and / or mechanically finishing the 3D printed object, like removing scraps and / or smoothing.

[0133] In a fourth aspect, the present disclosure refers to a 3D printed object obtained by the 3D printing method described above.

[0134] The 3D printed objects of the fourth aspect has good optical properties, like low clarity, high haze and high transparency, in combination with a good balance of mechanical properties, low warpage and shrinkage, and good layer adhesion.

[0135] In consideration of the optical properties, like low clarity, high haze and high transparency, the 3D printed object of the instant disclosure secures an efficient and uniform, light diffusion and is particularly suitable as light cover.

[0136] The features describing the subject matter of the present disclosure are not inextricably linked to each other. Hence, preferred ranges of one feature may be combined with more or less preferred ranges of a different feature, independently from their level of preference.EXAMPLES

[0137] The following examples are given to illustrate the present invention without limiting purpose.

[0138] CHARACTERIZATION METHODS : the following methods are used to determine the properties indicated in the description, claims and examples.

[0139] Melt Flow Rate: Determined according to the method ISO 1133-1 :2011 (230°C / 2.16 kg).

[0140] Solubility in xylene at 25°C: 2.5 g of polymer sample and 250 ml of xylene are introduced in a glass flask equipped with a refrigerator and a magnetic stirrer. The temperature is raised in 30 minutes up to 135°C. The obtained clear solution is kept under reflux and stirring for further 30 minutes. The solution is cooled in two stages. In the first stage, the temperature is lowered to 100°C in air for 10 to 15 minute under stirring. In the second stage, the flask is transferred to a thermostatically controlled water bath at 25°C for 30 minutes. The temperature islowered to 25°C without stirring during the first 20 minutes and maintained at 25°C with stirring for the last 10 minutes. The formed solid is filtered on quick filtering paper (eg. Whatman filtering paper grade 4 or 541). 100 ml of the filtered solution (SI) is poured in a previously weighed aluminum container, which is heated to 140°C on a heating plate under nitrogen flow, to remove the solvent by evaporation. The container is then kept on an oven at 80°C under vacuum until constant weight is reached. The amount of polymer soluble in xylene at 25°C is then calculated. XS(I) and XSA values are experimentally determined. The fraction of component (B) soluble in xylene at 25 °C (XSB) can be calculated from the formula:XS = W(A)X(XSA) + W(B)X(XSB) wherein W(A) and W(B) are the relative amounts of components (A) and (B), respectively, and W(A)+ W(B)=1.

[0141] Ethylene content of propylene-ethylene copolymers by NMR:13C NMR spectra were acquired on a Bruker AV-600 spectrometer equipped with cryoprobe, operating at 160.91 MHz in the Fourier transform mode at 120°C. The peak of the SPP carbon (nomenclature according to “Monomer Sequence Distribution in Ethylene-Propylene Rubber Measured by 13C NMR. 3. Use of Reaction Probability Mode”, C. J. Carman, R. A. Harrington and C. E. Wilkes, Macromolecules, 1977, 10, 536) was used as internal reference at 29.9 ppm. The samples were dissolved in l,l,2,2-tetrachloroethane-d2 at 120°C with a 8 % wt / v concentration. Each spectrum was acquired with a 90° pulse, 15 seconds of delay between pulses and CPD to remove 1H-13C coupling. 512 transients were stored in 32K data points using a spectral window of 9000 Hz. The assignments of the spectra, the evaluation of triad distribution and the composition were made according to Kakugo (“Carbon- 13 NMR determination of monomer sequence distribution in ethylene-propylene copolymers prepared with 8-titanium trichloride- diethylaluminum chloride” M. Kakugo, Y. Naito, K. Mizunuma and T. Miyatake, Macromolecules, 1982, 15, 1150) using the following equations:PPP = 100 Tpp / S PPE = 1OO TP8 / S EPE = 100 T88 / SPEP = 100 SPP / S PEE= 100 SP5 / S EEE = 100 (0.25 Sy8+0.5 S88) / SS = TPP + TP8 + T88 + SPP + Sp8 + 0.25 Sy8 + 0.5 S88

[0142] The molar percentage of ethylene content was evaluated using the following equation:E% mol = 100 * [PEP+PEE+EEE]

[0143] The weight percentage of ethylene content was evaluated using the following equation:100 * E% mol * MWEE% wt. = >E% mol * MWE+ P% mol * MWp

[0144] where P% mol is the molar percentage of propylene content, while MWE and MWp are the molecular weights of ethylene and propylene, respectively.

[0145] Ethylene and butene-1 content of propylene terpolymers by NMR:13C NMR spectra were acquired on a Bruker AV-600 spectrometer equipped with cryoprobe, operating at 150.91 MHz in the Fourier transform mode at 120°C. The peak of the S88 carbon (nomenclature according to “Monomer Sequence Distribution in Ethylene-Propylene Rubber Measured by 13C NMR. 3. Use of Reaction Probability Mode”, C. J. Carman, R. A. Harrington and C. E. Wilkes, Macromolecules, 1977, 10, 536) was used as internal reference at 29.9 ppm. The samples were dissolved in l,l,2,2-tetrachloroethane-d2 at 120°C with a 8 % wt / v concentration. Each spectrum was acquired with a 90° pulse, 15 seconds of delay between pulses and CPD to remove 1H-13C coupling. 512 transients were stored in 65K data points using a spectral window of 9000 Hz. The assignments of the spectra, the evaluation of triad distribution and the composition were made based on Kakugo (“Carbon- 13 NMR determination of monomer sequence distribution in ethylenepropylene copolymers prepared with 8-titanium trichloride- diethylaluminum chloride” M. Kakugo, Y. Naito, K. Mizunuma and T. Miyatake, Macromolecules, 1982, 15, 1150) using the following equations:PPP = lOO Iio / S PPE = 100 I6 / S EPE = 100 I5 / SBBB = 100 E / S BBE = 100 I2 / S EBE = 100 III / SXEX = 100 I12 / S XEE = 100 (Ii +I4) / S EEE = 100 (0.5I9+0.25(l7+Is)) / SS — Il+l2+l3+l4+l5+l6+0.25l7+0.25l8+0.5I9+Iio+Il 1+112

[0146] Wherein X is propylene (P) or butene- 1 (B) and Ii to I12 are the areas of the corresponding carbon atoms as reported in the following table:

[0147] The molar content of ethylene, propylene and butene- 1 was obtained using the following equation:E% mol = 100 * [XEX+XEE+EEE]P% mol = 100 * [PPP+PPE+EPE]B% mol = 100 * [BBB+BBE+EBE]

[0148] The weight percent of ethylene was determined using the following equation:100 * E% mol * MWEE% wt. = -(E% mol * MWE )+ (P% mol * MWp)+(B%mol * MWB)

[0149] where P% mol and B% mol are as defined above and MWE, MWP and MWB are the molecular weights of ethylene, propylene and butene- 1 respectively. The weight percent of butene- 1 is determined using an analogous equation.

[0150] Melting temperature: determined according to ISO 11357-3:2018, at scanning rate of 20°C / min both in cooling and heating, on a sample of weight between 5 and 7 mg., under inert N2 flow. Instrument calibration made with Indium.

[0151] Density: determined according to ISO 1183-l / A:2019 at 23°C.

[0152] Tensile properties: determined according to ISO 527-1,-2:2019 on specimens according to ISO 20753-Al :2018-10.

[0153] Charpy impact strength: determined according to ISO 179-1:2010 eA on on injection molded specimens Type B2 according to ISO 20753-Al :2018-10.

[0154] Heat deflection temperature: ISO 75B-l,-2, 0.45 MPa, 48h, unannealed.

[0155] Haze: the method determines the percentage of transmitted light that deviates from the incident beam by forward scattering when passing through the specimen and is in accordance with ASTM D1003 (non-compensated method). Only light deviating more than 2.5° is considered to be haze. The haze value is determined using a hazemeter such as BYK-Gardner Haze-Gard Plus, or an equivalent instrument with CIE illuminant C and an integrated sphere geometry in accordance with ASTM DI 003. Imm-thick plaques are conditioned at 23±2°C and 50±10% humidity for 24h prior to testing. The plaques are placed in contact with the haze port and measurements are made at the center of the test specimen. The haze value is automatically calculated by the test instrument based on the following formula:Haze [%] = Td / TtX 100 wherein Td is the diffuse transmittance and Tt is the total transmittance.

[0156] Clarity: the method determines the percentage of transmitted light that deviates from the incident beam by forward scattering when passing through the specimen in accordance with ASTM DI 003. Only light deviating less than 2.5° is considered to be clarity. The haze value is determined using a hazemeter such as BYK-Gardner Hazegard Plus, or an equivalent instrument with CIE illuminant C and an integrated sphere geometry in accordance with ASTM DI 003. Imm- thick plaques are conditioned at 23±2°C and 50±l 0% humidity for 24h prior to testing. The plaques are placed in front of the light source and measurements are made at the center of the test specimen. The clarity value is automatically calculated by the test instrument based on the following formula: Clarity [%] = Ic— IR / IC+IR 100

[0157] wherein Icis the Intensity of the center sensor and IR is the Intensity of the ring sensor.

[0158] Total transmittance: the method determines the ratio of light transmitted through a specimen to the flux incident upon it according to ISO 13468-1:2019. The total transmittance is determined using a hazemeter such as BYK-Gardner Hazegard Plus, or an equivalent instrument with CIE illuminant C and an integrated sphere geometry in accordance with ASTM D1003 / ISO 13468-1 :2019. Imm-thick plaques are conditioned at 23±2°C and 50±10% humidity for 24h prior to testing. The plaques are placed in contact with the haze port and measurements are made at thecenter of the test specimen. The haze value is automatically calculated by the test instrument based on the following formula:Total transmittance [%] = IT / I}x 100 wherein IT is the intensity of the transmitted light and h is the intensity of the initial light beam.

[0159] Warpage: determined on a 3D printed frame adapted from M. Spoerk et al., Macromol. Mater. Eng. 2017, 302, 1700143, as illustrated in FIG.l. Printing conditions are reported in Table 3 below. The infill orientation alternates a +45° layer to a -45° layer, wherein at +45° the infill orientation is parallel to the diagonal (d) between corner 1 and corner 3 (see FIG.1), and at -45° the infill orientation is perpendicular to the diagonal (d). The first layer that adheres to the build plate has an infill orientation of +45°. The 3D printed frame was removed from the build plate readily after printing, and tempered at 80°±5°C in vacuum for 24±1 hours. After allowing it to cool down to 25°C, the 3D printed frame was fixed to an horizontal surface, at an horizontal distance of 2 mm from corner 1, with a 2 mm diameter rod as illustrated in FIG.2. The warpage height (h) was measured as the distance between the horizontal surface to which the frame is fixed and the lower edge of corner 3 (FIG.2), diagonal to the fixed corner 1. Corner 3 is subsequently fixed to the horizontal surface, and the length of the diagonal (d) between the edges of corners 1 and 3 was measured. The percent warpage was calculated using the equation:Warpage [%] = 100 x , -'-rp-ge height h1°L Jlength of diagonal a

[0160] Five specimen were printed for each filament tested; tables report the mean values.

[0161] RAW MATERIALS

[0162] TERPO: is a propylene / ethylene / butene-1 terpolymer containing 1.1 wt.% ethylene units and 5.3 wt.% of butene-1 units, and having a xylene soluble fraction at 25°C of 5.0 wt.%. The polymer was prepared according to the polymerization process described in Example 1 of WO2014 / 198459. The polymer particles obtained from the reactor were mixed in the molten state with 0.4 wt.% of Millad® NX® 8000, 0.05 wt.% of calcium stearate, 0.1 wt.% of glyceryl monostearate (GMS 90), 0.1 wt.% of Irgafos® 168 and 0.05 wt.% of an antioxidant. The extruder was operated under nitrogen atmosphere at a rotational speed of 250 rpm and a temperature of 200-250°C. The properties of the obtained material are reported in Table 1.

[0163] RACO: propylene-ethylene copolymer containing 3.0 wt.% of ethylene units, having a xylene soluble fraction at 25°C of 6 wt.%. The propylene-ethylene copolymer was produced intwo loop reactors operated at a temperature of 72°C, in the presence of a Ziegler-Natta catalyst system. Hydrogen was used at a concentration of ca.1500 ppm in both reactors. The polymer particles obtained from the reactor were mixed in the molten state with 0.18 wt.% of DMDBS, 0.05 wt.% of calcium stearate, 0.05 wt.% of glyceryl monostearate (GMS 90), 0.1 wt.% of Irgafos® 168 and 0.05 wt.% of an antioxidant. The extruder was operated under nitrogen atmosphere at a rotational speed of 250 rpm and a temperature of 200-250°C. The properties of the obtained material are reported in Table 1.Table 1

[0164] Moplen HF501N: a propylene homopolymer from LyondellBasell, having a melt flow rate of 12 g / 10 mm. (ISO1133; 230°C / 2.16Kg) and tensile modulus (ISO 527-1,-2:2019) of 1550 MPa.

[0165] Kraton™ G1643V: from Kraton Corp., a linear styrene triblock copolymer based on styrene and ethylene / butylene containing 30 wt.% of polystyrene, having MFR (ASTM D1238; 230°C, 2.16 Kg) of 19 g / lOmin. and Shore A value (ASTM D2240, 30 sec.) of 52.

[0166] GF EC10 636: ThermoFlow® 636 from Johns Manville, chopped E-glass fibers having fiber diameter of 10 pm and chopped strands length of 4mm.

[0167] Bondyram® 1101: from Polyram Plastic Industries LTD, is a maleic anhydride modified polypropylene compound with a maleic anhydride content (FTIR) of 1 wt.% and a melt flow index (ISO 1133, 190°C / 2.16 Kg) of 170 g / lOmin.

[0168] DMDBS: l,3:2,4-bis(3,4-dimethyldibenzylidene) sorbitol, Millad 3988 supplied by Milliken Chemical.

[0169] Millad® NX® 8000: a clarifying agent supplied by Milliken Chemical.

[0170] Irgafos® 168: a processing stabilizer supplied by BASF.

[0171] Examples El to E3 and comparative example CE4

[0172] Filaments of diameter 2.85±0.02mm were produced from the polyolefin compositions of Table 2 on a twin-screw extruder LAB LINE Model E 20 P from Collin, equipped with a round die, operated in the following conditions:- feeding zone temperature: 40°C- zone 1 -4 temperature: 185°C- screw speed: 54 rpm- melt pressure: 40 bar- throughput: 3.08 kg / h- haul-off speed: 9.8 m / min

[0173] The extruded polymer strand was withdrawn, water cooled and rolled up on a spool.

[0174] The filaments were fed to a UltiMaker 2 3D printer, and 3D printed test specimens having the shape and orientation illustrated in figures from FIG.3A to FIG.3C were produced. Printing conditions are illustrated in Table 3 below.

[0175] Test results on the 3D printed specimen are reported in Table 2.Table 2Table 3

[0176] Examples E5 to E7 and comparative examples CE8 and CE9

[0177] Filaments of diameter 2.85±0.02mm were produced from the polyolefin compositions of Table 4 on a twin-screw extruder LAB LINE Model E 20 P from Collin, equipped with a round die, operated in the same conditions as Example El . The extruded polymer strand was withdrawn, water cooled and rolled up on a spool.

[0178] The filaments were fed to a UltiMaker 2 3D printer, and 3D printed test specimens having the shape and orientation illustrated in from FIG.3 A to 3C were produced. Printing conditions are illustrated in Table 2 above.

[0179] Test results on the 3D printed specimen are reported in Table 4.Table 4

Claims

CLAIMSWhat is claimed is:

1. A filament for extrusion-based additive manufacturing comprising a polyolefin composition (I) comprising:(A) from 55 to 85% by weight of a copolymer of propylene with ethylene and / or a C4-C10 alpha-olefin having a melt flow rate MFR(A) of from 5. O to 50 g / lOmin (ISO 1133-1 :2011; 230°C / 2.16 kg);(B) from 10 to 30% by weight of a styrene or alpha-methylstyrene block copolymer;(C) from 1 to 20% by weight of glass fibers; and(D) from 0 to 2% by weight of a compatibilizer, wherein the amounts of components (A), (B), (C) and (D) are based on the total weight of the polyolefin composition (I).

2. The filament according to claim 1 , wherein the polyolefin composition (I) comprises from 60 to 80% by weight of component (A), from 17 to 27% by weight of component (B), from 2.0 to 17% by weight of component (C) and from 0.1 to 1.5 of component (D), wherein the amounts of components (A), (B), (C) and (D) are based on the total weight of the polyolefin composition (I).

3. The filament according to claim 1 or 2, wherein the alpha-olefin comprised in the propylene copolymer (A) is selected from butene- 1 and hexene- 1.

4. The filament according to any one of the preceding claims, wherein component (A) is selected from:(Al) a propylene / ethylene copolymer having:- an ethylene content of up to and including 4.0% by weight, based on the weight of the propylene / ethylene copolymer; and- a solubility in xylene at 25°C equal to or lower than 10% by weight, based on the weight of the propylene / ethylene copolymer;(A2) a propylene / ethylene / butene-1 terpolymer having:- a content of units deriving from ethylene of from 0.5 to 2.0% by weight and a content of units derived from butene- 1 of from 3.5 to 7.0% by weigh, based on the weight of the propylene / ethylene / butene-1 terpolymer; and- a solubility in xylene at 25°C equal to or lower than 7.0% by weight, based on the weight of the propylene / ethylene / butene-1 terpolymer; and(A3) combinations thereof.

5. The filament according to claim 4, wherein the propylene / ethylene copolymer (Al) has:- an ethylene content of from 0.4 to 4.0 % by weight, preferably from 0.5 to 3.5 % by weight, based on the weight of the propylene / ethylene copolymer; and- a solubility in xylene at 25°C ranging from 0.1 to 10% by weight, preferably from 1.0 to 8.0 % by weight, based on the weight of the propylene / ethylene copolymer.

6. The filament according to claim 4, wherein the propylene / ethylene / butene-1 terpolymer (A2) has:- a content of units deriving from ethylene of from 0.7 to 1.8% by weight, preferably from 0.9 to 1.5% by weight, and a content of units derived from butene- 1 of from 4.0 to 6.5% by weigh, preferably from 4.5 to 6.0% by weight, based on the weight of the propylene / ethylene / butene-1 terpolymer; and- a solubility in xylene at 25°C of from 2.0 to 7.0% by weight, preferably from 3.0 to 6.0% by weight, based on the weight of the propylene / ethylene / butene-1 terpolymer.

7. The filament according to any one of the preceding claims, wherein the component (A) has at least one of the following properties, preferably all:- tensile modulus (ISO 527-1,-2) greater than 1000 MPa, preferably in the range of from 1100 to 1400 MPa; and / or- elongation at yield (ISO 527-1,-2) in the range of from 10 to 20%; and / or- Charpy impact strength (ISO 179, 23°C, Type 1, Notch A) in the range of from 4 to 10 kJ / m2; and / or- heat deflection temperature B (0.45 MPa, unannealed, ISO 75B-l,-2) in the range of from 72 to 80°C.

8. The filament according to any one of the preceding claims, wherein component (B) is a styrene block copolymer comprising up to and including 40% by weight of polystyrene, preferably from 10% to 35% by weight, more preferably from 15% to 30% by weight, based on the weight of the block copolymer.

9. The filament according to any one of the preceding claims, wherein component (B) is selected from the group consisting of polystyrene-polybutadiene-poly styrene (SBS), polystyrene-poly(ethylene-butylene)-polystyrene (SEBS), polystyrene-poly(ethylene- propylene)-polystyrene (SEPS), polystyrene-polyisoprene-polystyrene (SIS), polystyrene- poly(isoprene-butadiene)-polystyrene (SIBS) and mixtures thereof; polystyrene- poly(ethylene-butylene)-polystyrene (SEBS) being preferred.

10. The filament according to any one of the preceding claims, wherein the glass fibers (C) have diameter ranging from 5 to 20 microns, preferably from 8 to 15 microns; and length equal to or lower than 10 mm, preferably ranging from 0.1 to 10 mm, more preferably from 1 to 8 mm, still preferably from 2 to 7 mm, still preferably from 3 to 6 mm.

11. The filament according to any one of the preceding claims, wherein the compatibilizer (D) is a polyethylene and / or a polypropylene grafted with maleic anhydride (MAH-g-PP and / or MAH-g-PE).

12. The filament according to any one of the preceding claims, wherein the polyolefin composition (I) further comprises up to and including 5.0% by weight, preferably from 0.01 to 3.0% by weight, based on the total weight of the polyolefin composition (I), of a component (E) being an additive preferably selected from the group consisting of antistatic agents, antioxidants, light stabilizers, slipping agents, anti-acids, melt stabilizers, clarifiers, nucleating agents, pigments and combinations thereof.

13. The filament according to any one of the preceding claims having diameter ranging from 1.00 to 4.00 mm, preferably from 1.50 to 3.00 mm.

14. A process to prepare a filament for extrusion-based additive manufacturing comprising the steps of:(a) providing the polyolefin composition (I) or the components from (A) to (D), and optionally (E), as described in any one of claims from 1 to 12;(b) extruding the polyolefin composition (I) or the components from (A) to (D), and optionally (E), through a die, thereby obtaining a filament; and(c) cooling the filament, and optionally rolling up the filament on a spool.

15. The process of claim 14, wherein the die of step (b) is a round die.

16. A 3D printing method comprising the steps of:(i) providing a filament according to any one of the claims 1 to 13;(ii) configuring a 3D printer with an extruder assembly, a heated extruder nozzle and, optionally but preferably, a build platform;(iii) extruding the filament through the heated extruder nozzle in a controlled manner, thereby building successive printed layers of the desired object based on a digital 3D model;(iv) allowing each printed layer to cool and solidify before proceeding to the next layer.

17. The 3D printing method according to claim 16, wherein in step (ii) the extruder nozzle is heated to a predetermined temperature suitable for melting the filament and, optionally, by heating the build platform to enhance adhesion.

18. The 3D printing method according to claim 16 or 17, wherein step (iii) comprises building successive printed layers of the desired object on the built platform.

19. The 3D printing method according to any one of claims from 16 to 18, further comprising a step (v) of removing the build platform from the 3D printed object and / or mechanically finishing the 3D printed object.

20. A 3D printed object obtained by the 3D printing method as described in any one of claims from 16 to 19.

21. The 3D printed object of claim 20, wherein the object is a light cover.

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