Flame retardant polyolefin material for additive manufacturing

Abstract

Flame retardant polyolefin composition for additive manufacturing comprising: a) from 5 to 30 wt.% of an heterophasic propylene copolymer; b) from 1 to 25 wt.% of a propylene / ethylene / C4-C10alpha-olefin terpolymer; c) from 1 to 20 wt.% of an elastomeric copolymer of ethylene with propylene or a C4- C10alpha-olefin;d) from 1 to 25 wt.% of a reinforcing material; and e) at least 15 wt.% of a flame retardant material.

Description

TITLEFLAME RETARDANT POLYOLEFIN MATERIAL FOR ADDITIVE MANUFACTURINGFIELD OF THE INVENTION

[0001] The present disclosure relates to the field of additive manufacturing, in particular it relates to a flame-retardant polyolefin material suitable for 3D printing and to a 3D printing process making use of the material.BACKGROUND OF THE INVENTION

[0002] Plastic flame retardancy is crucial in various applications where fire safety is a significant concern.

[0003] Flame-retardant plastics are used in the housings of electronic devices, circuit boards, connectors, and other electrical components to prevent fire hazards caused by electrical faults. Flame-retardant coatings are essential for wires and cables to prevent the spread of fire along electrical installations.

[0004] In the field of building and construction, flame-retardant materials are used in insulation, wiring, pipes, and structural components to reduce the risk of fire spread in buildings and ensure compliance with building codes.

[0005] In vehicles, flame-retardant plastics are used not only in electrical systems, but also in interior components, and under-the-hood parts, to enhance passenger safety and meet stringent fire safety standards. When used for unpainted visible parts, flame retardant plastic materials should provide items with good surface quality.

[0006] Flame retardant plastic materials must be convertible into final items by different manufacturing processes, like extrusion, injection molding, etc. and several flame-retardant plastics have been developed tailoring material properties to suit the different process conditions.

[0007] Plastic additive manufacturing has become highly relevant in various industries due to its versatility, cost-effectiveness, and ability to produce complex designs. Intricate and complex geometries that would be difficult or impossible to achieve with traditionalmanufacturing techniques like injection molding can be produced by 3D printing. This opens up new possibilities for design and innovation.

[0008] Furthermore, 3D printing is an additive process that builds objects layer by layer. This results in significantly less material waste, making additive manufacturing an environmental friendly process.

[0009] A wide range of plastics can be used in 3D printing, each with unique properties suited to different applications. Common materials include ABS for its durability, PLA for its eco-friendliness, and PET for its food-safe properties

[0010] Also polyolefin-based 3D printing materials are known in the art. For instance, polyolefin compositions for additive manufacturing containing an heterophasic propylene polymer, 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. Warpage occurs due to material shrinkage while 3D printing, which causes the comers of the print to lift and detach from the build plate, thereby compromising the planarity of the printed object.

[0011] Filaments for 3D printing with reduced warpage made from propylene / ethylene / butene-1 terpolymers are also known from WO2017 / 182211.

[0012] Beyond flatness, also overhangs are challenging in additive manufacturing, particularly in fused deposition modeling 3D printing. Overhangs refer to parts of a model that extend outward beyond the previous layer without direct support underneath. To be fully satisfactory, 3D printing plastic materials should allow the printability of overhangs without collapsing.

[0013] In this frame, there is still the need of a flame-retardant plastic material suitable for being processed by additive manufacturing, i.e. a plastic material having low warpage and shrinkage, which also exhibit a good mechanical profile, like high impact resistance and high tensile strength, and which can be printed into articles having good surface quality and overhangs printability.

[0014] It has been surprisingly found that glass-fiber filled polyolefin compositions containing one or more heterophasic propylene copolymers, in combination with one or more propylene terpolymers and one or more ethylene / alpha-olefin copolymers can beloaded with more than 15 wt.% of one or more flame retardants and used in additive manufacturing to obtain 3D printed objects having the desired properties, like good balance of mechanical properties, low warpage and shrinkage, and excellent surface quality and overhangs printability.SUMMARY OF THE INVENTION

[0015] In a first aspect, the present disclosure provides a flame retardant polyolefin composition for additive manufacturing comprising, based on the total weight of the flame retardant polyolefin composition:

[0016] a) from 5 to 30 wt.% of an heterophasic propylene copolymer;

[0017] b) from 1 to 25 wt.% of a propylene / ethylene / C4-C10alpha-olefin terpolymer;

[0018] c) from 1 to 20 wt.% of an elastomeric copolymer of ethylene with propylene or a C4-C10alpha-olefin;

[0019] d) from 1 to 25 wt.% of a reinforcing material; and

[0020] e) at least 15 wt.% of a flame retardant material.

[0021] In a further aspect, the present disclosure refers to a filament, bead, pellet or powder for additive manufacturing comprising the flame retardant polyolefin composition of the first aspect.

[0022] In a still further aspect, the present disclosure refers to an additive manufacturing process to obtain a flame retardant object, the process comprising the steps of:

[0023] (i) providing a filament or pellet comprising the flame retardant polyolefin composition of the first aspect;

[0024] (ii) providing a 3D printer with an extruder assembly, a heated extruder nozzle and a build platform;

[0025] (iii) heating the filament or pellet in the extruder assembly, thereby obtaining an at least partially molten flame retardant printing material; and

[0026] (iv) extruding the at least partially molten flame retardant printing material through the heated extruder nozzle depositing it layer by layer onto the build platform.

[0027] In a further aspect, the present disclosure refers to a flame retardant 3D printed article comprising the flame retardant polyolefin composition of the first aspect.

[0028] The flame retardant polyolefin composition of the present disclosure has a good balance of mechanical properties, like high tensile modulus and high impact resistance, and results in 3D printed articles having low warpage and shrinkage, excellent surface quality and overhangs printability.

[0029] 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 DESCRIPTION OF THE DRAWINGS

[0030] FIG.1 provides a schematic representation of the infill orientation for 45° 3D printed specimens of Examples E1-E2 and Comparative Example CE3. The infill orientation of adjacent layers is mutually perpendicular, i.e. the first layer is printed at +45° and the adjacent at -45°.

[0031] FIG. 2 provides a schematic representation of the 3D printed frame used to determine warpage.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 two different monomers and the term “terpolymers” refers to polymers obtained by the intentional polymerization of three different comonomers. The term copolymer does not include terpolymers.

[0039] In a first aspect, the present disclosure provides a flame retardant polyolefin composition for additive manufacturing comprising, based on the total weight of the flame retardant polyolefin composition:

[0040] a) from 5 to 30 wt.% of an heterophasic propylene copolymer;

[0041] b) from 1 to 25 wt.% of a propylene / ethylene / C4-C10alpha-olefin terpolymer;

[0042] c) from 1 to 20 wt.% of an elastomeric copolymer of ethylene with propylene or a C4-C10alpha-olefin;

[0043] d) from 1 to 25 wt.% of a reinforcing material; and

[0044] e) at least 15 wt.% of a flame retardant material.

[0045] Preferably, the flame retardant polyolefin composition comprises, based on the total weight of the flame retardant polyolefin composition:

[0046] a) from 10 to 20 wt.% of an heterophasic propylene copolymer; and / or

[0047] b) from 5 to 20 wt% of a propylene / ethylene / C4-C10alpha-olefin terpolymer; and / or

[0048] c) from 5 to 15 wt.% of an elastomeric copolymer of ethylene with propylene ora C4-C10alpha-olefin; and / or

[0049] d) from 10 to 20 wt.% of a reinforcing material; and / or

[0050] e) from 20 to 40 wt.% of a flame retardant material.

[0051] The individual components from a) to e) of the flame retardant polyolefin compositions are defined in greater detail below. The individual components may be comprised in the flame retardant polyolefin composition in any combination.

[0052] Heterophasic propylene copolymers are copolymers comprising immiscible phases, like a continuous phase, the matrix, in which a discontinuous phase, the elastomeric or rubbery phase, is dispersed. The elastomeric phase forms inclusions in the matrix, said inclusions being visible by high resolution microscopy, like electron microscopy or scanning force microscopy.

[0053] Preferably, the heterophasic propylene copolymer a) has one or more of the following properties, preferably all:

[0054] a.i) Vicat softening temperature in the range of from 50° to 130°C (A50, ISO 306:2022); and / or

[0055] a.ii) melting temperature in the range of from 135°C to 165°C (ISO 11357-3:2018); and / or

[0056] a.iii) melt flow rate MFR(a) in the range of from 2 to 50 g / 10min, preferably from 5 to 25 g / 1 Omin (ISO 1133-1 :2011 , 230°C / 2.16 kg); and / or

[0057] a.iv). tensile modulus in the range of from 400 to 1200 MPa, preferably from 600 to 1000 MPa (ISO 527-1 ,-2:2019); and / or

[0058] a.v) Charpy impact strength at 23°C in the range of from 20 to 70 kJ / m2, preferably from 35 to 60 kJ / m2 (ISO 179-1:2010 1eA).

[0059] The heterophasic propylene copolymer a) preferably comprises, based on the weight of the heterophasic propylene copolymer a):

[0060] - from 15 to 70 wt.% of a polymer fraction (A) comprising a propylene homopolymer or a copolymer of propylene with ethylene or a C4-C10alpha-olefin containing up to 10 wt.%, based on the weight of the fraction (A), of polymerized units deriving from ethylene or the alpha-olefin, the fraction (A) having solubility in xylene at 25°C XS(A) lower than 10 wt.%, based on the weight of fraction (A), wherein the xylene soluble fraction at 25°C is determined according to the method described in the examples section; and

[0061] - from 30 to 85 wt.% of a copolymer fraction (B) comprising a copolymer of ethylene with propylene or a C4-C10alpha-olefin, the copolymer fraction (B) containing from 20 to 75 wt.%, preferably from 35 to 70 wt.%, of polymerized units derived fromethylene, based on the weight of the copolymer fraction (B), wherein the copolymer fraction (B) is different from component c).

[0062] Fraction (A) forms the continuous matrix phase and copolymer fraction (B) is the dispersed phase.

[0063] Preferably, the C4-C10alpha-olefin of the polymer fraction (A) and of the copolymer faction (B) is independently selected from butene-1, hexene-1 and octene-1.

[0064] In a preferred embodiment, the heterophasic propylene copolymer a) comprises, based on the weight of the heterophasic propylene copolymer a):

[0065] - from 45 to 65 wt.%, preferably from 50 to 60 wt.%, of a fraction (A) comprising a propylene homopolymer or a copolymer of propylene with ethylene or a C4-C10alpha-olefin containing up to 10 wt.%, based on the weight of the fraction (A), of polymerized units deriving from ethylene or the alpha-olefin, the fraction (A) having solubility in xylene at25°CXS(A) lower than 10 wt.%, based on the weight of fraction (A), wherein the xylene soluble fraction at 25°C is determined according to the method described in the examples section; and

[0066] - from 35 to 55 wt.%, preferably from 40 to 50 wt.%, of a copolymer fraction (B) comprising a copolymer of ethylene with a C4-C10alpha-olefin (B1) and an ethylene / propylene copolymer (B2), wherein the weight ratio (B1) / (B2) is from 2:1 to 1:2 and wherein the copolymer fraction (B) contains from from 35 to 75 wt.%, preferably from 45 to 70 wt.%, of polymerized units derived from ethylene, based on the weight of the copolymer fraction (B).

[0067] Copolymers (B1) and (B2) are different from component c).

[0068] Polymer fraction (A) preferably comprises a propylene homopolymer and has solubility in xylene at 25°C XS(A) lower than 5 wt.%, preferably equal to or lower than 3 wt.%, based on the weight of fraction (A).

[0069] Less preferably, fraction (A) comprises a copolymer of propylene with ethylene or with a C4-C10alpha-olefin selected from butene-1 and hexene-1.

[0070] Preferably, polymer fraction (A) has melt flow rate MFR(A) in the range of from 30 to 100 g / 10min, preferably from 50 to 80 g / 10min (ISO 1133-1:2011 (230°C / 2.16 kg).

[0071] Preferably, the copolymer (B1) is an ethylene / butene-1 copolymer, more preferably comprising from 60 to 80 wt.% of polymerized units deriving from ethylene, based on the weight of copolymer (B1).

[0072] Preferably, the weight ratio (B1) / (B2) is in the range from 1.5:1 to 1:1.

[0073] The heterophasic propylene copolymer a) optionally has a xylene soluble fraction at 25°C XS(a) in the range of from 25 to 50 wt.%, preferably from 30 to 40 wt.%, based on the weight of the heterophasic propylene copolymer a), wherein the xylene soluble fraction at 25°C is determined according to the method described in the examples section.

[0074] Optionally, the intrinsic viscosity of the fraction soluble in xylene at 25°C XSIV(a) of the heterophasic propylene copolymer a) is in the range of from 1.5 to 3.5 dl / g, wherein the intrinsic viscosity is determined according to the method described in the examples section.

[0075] Heterophasic propylene copolymers suitable for use as component a) are known in the art and are available on the market, e.g. under the tradenames of Adstif, Moplen or Hi fax supplied by LyondellBasell.

[0076] The heterophasic propylene copolymer a) is preferably prepared by sequential polymerization stages, with each subsequent polymerization stage except the first one being conducted in the presence of the polymeric material formed in the immediately preceding polymerization stage.

[0077] Preferably, the polymer fraction (A) is prepared in a first polymerization stage and the copolymer fraction (B) is prepared in a second polymerization stage. The polymerization stage to prepare the polymer fraction (A) is carried out in at least one polymerization reactor and the polymerization stage to produce the copolymer fraction (B) is carried out at least one, preferably at least two, polymerization reactor(s). The amounts of polymer fraction (A) and of copolymer fraction (B) correspond to the split between the polymerization stages. The amounts of the copolymer (B1) and of the copolymer (B2) correspond to the split between the respective polymerization reactors.

[0078] The polymerization stages are preferably carried out in the presence of a Ziegler-Natta catalyst system. According to a preferred embodiment, all polymerization stages are carried out in the presence of a catalyst comprising the reaction product of:

[0079] (1) a solid catalyst component comprising Ti, Mg, Cl, and at least an internal electron donor compound;

[0080] (2) an alkylaluminum compound and,

[0081] (3) optionally but preferably, an external electron-donor compound selected from aromatic acid esters, such as alkyl benzoates, and silicon compounds containing at least one Si-OR bond, where R is a hydrocarbon radical.

[0082] The solid catalyst component (1) preferably comprises TiCk 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).

[0083] 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.

[0084] Preferred donors are the esters of phthalic acids such as those described in EP45977A2 and EP395083A2, in particular di-isobutyl phthalate, di-n-butyl phthalate, di-n-octyl phthalate, diphenyl phthalate, benzylbutyl phthalate and combinations thereof.

[0085] 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 WOOO / 55215, and esters of succinic acids such as those disclosed WOOO / 63261.

[0086] 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.

[0087] In some embodiments, the internal donor is selected from 1 ,3-diethers such as those described in EP361493, EP728769 and WO02 / 100904. Representative examples of dieters are 2-methyl-2-isopropyl-1,3-dimethoxypropane, 2,2-diisobutyl-1 ,3-dimethoxypropane, 2-isopropyl-2-cyclopentyl-1 ,3-dimethoxypropane, 2-isopropyl-2-isoamyl-1 ,3-dimethoxypropane, and 9,9-bis(methoxymethyl)fluorene.

[0088] 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.

[0089] Preferred magnesium halide support is magnesium dihalide.

[0090] 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.

[0091] The preparation of catalyst components according to a general method is described for example in Patent Applications US4,399,054, US4,469,648 and W098 / 44009A1. Preferred methods for the preparation of the solid catalyst component (1) are described in EP395083A2. The particles of solid component (1) may have substantially spherical morphology and average diameter ranging between 5 and 150pm, preferably from 20 to 100pm and more preferably from 30 to 90pm. As particles having substantially spherical morphology, those are meant wherein the ratio between the greater axis and the smaller axis is equal to or lower than 1.5 and preferably lower than 1.3.

[0092] 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.

[0093] In preferred 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. The external electron donor compound (3) is used in such an amount to give a molar ratio between the organoaluminium compound and said external electron donor compound (3) of from 0.1 to 200, preferably from 1 to 100 and more preferably from 3 to 50.

[0094] Preferred silicon compounds are selected among methylcyclohexyldimethoxysilane (C-donor), dicyclopentyldimethoxysilane (D-donor) and mixtures thereof.

[0095] All the polymerization stages preferably occur in gas phase. The reaction temperatures of the polymerization stages for the preparation of the polymer fraction (A) and the copolymer fraction (B) can be the same or different, and are preferably from 40° to 90°C. The pressure of each polymerization stage is independently selected from values ranging from 5 to 30 bar in gas phase. The residence time in each stage depends on the desired ratio between the fractions (A) and (B), and preferably ranges from 15 minutes to 8 hours.

[0096] Conventional molecular weight regulators known in the art, such as chain transfer agents (e.g. hydrogen orZnEt2), may be used.

[0097] The C4-C10alpha-olefin contained in the propylene / ethylene / C4-C10alpha-olefin terpolymer b) is preferably selected from butene-1 and hexene-1.

[0098] Particularly preferably, the propylene / ethylene / C4-C10alpha-olefin terpolymer b) is selected from:

[0099] b1) propylene / ethylene / butene-1 terpolymers containing from 0.5 to 7.0 wt.% of polymerized units derived from ethylene and from 2.0 to 17.0 wt.% of polymerized units derived from butene-1 , based on the total weight of the terpolymer b1),

[0100] b2) propylene / ethylene / hexene-1 terpolymers containing from 0.5 to 5.0 wt.% of polymerized units derived from ethylene and from 1.0 to 12.0 wt.% of polymerized units derived from hexene-1 , based on the total weight of the terpolymer b2), and

[0101] b3) a combinations thereof.

[0102] Preferably, the propylene / ethylene / C4-C10alpha-olefin terpolymer b) has one or more of the following properties, preferably all:

[0103] b.i) melt flow rate MFR(b) in the range of from 1 to 20 g / 10min, preferably from 3 to 10 g / 10min ((ISO 1133-1:2011, 230°C / 2.16 kg); and / or

[0104] b.ii) xylene soluble fraction at25°C in the range of from 4 to 25 wt.%, preferably from 6 to 15 wt.%, based on the weight of the terpolymer b), wherein the xylene soluble fraction is determined according to the method described in examples section; and / or

[0105] b.iii) Vicat softening temperature in the range from 105° to 120°C (A50, ISO 306:2022); and / or

[0106] b.iv) melting temperature in the range of from 125° to 143°C (ISO 11357-3:2018); and / or

[0107] b.v) Seal Initiation Temperature in the range of from 100° to 115°C, determined according to the method described in the example section.

[0108] The propylene / ethylene / C4-C10alpha-olefin terpolymers b) are available on the market and are preferably produced in a sequential polymerization process carried out in the gas phase in the presence of a Ziegler Natta catalyst as described in the foregoing. Suitable polymerization processes to obtain the propylene / ethylene / C4-C10alpha-olein terpolymers b) are described for instance in W003 / 031514A1, WO2017 / 021138A1 and W02024 / 028042A1.

[0109] Component c) is an elastomeric copolymer of ethylene with propylene or a C4-C10alpha-olefin, wherein the alpha olefin is preferably selected from butene-1, hexene-1 and octene-1. Preferably the component c) is an ethylene / octene-1 copolymer.

[0110] Optionally, the ethylene copolymer c) contains at most 80 wt.% of polymerized units derived from ethylene, preferably from 50 to 80 wt.% of units derived from ethylene, based on the weight of the ethylene copolymer c).

[0111] Optionally, the elastomeric copolymer of ethylene with propylene or a C4-ClOalpha-olefin has one or more of the following properties, preferably all:

[0112] c.i) density in the range of from 0.855 to 0.910 g / cm3, preferably from 0.860 to 0.880 g / cm3(ASTM D792); and / or

[0113] c.ii) melt index in the range of from 0.1 to 30 g / 10min, preferably from 3 to 15 g / 10min (ASTM D1238, 2.16Kg at 190°C); and / or

[0114] c.iii) Shore A value of from 50 to 90, preferably from 55 to 75 (ASTM D2240).

[0115] The elastomeric ethylene copolymers c) are commercially available, e.g. with the trademark Engage marketed by Dow, and are generally produced by polymerizing the relevant monomers with metallocene catalysts.

[0116] In the flame retardant composition the reinforcing material d) is preferably but not exclusively glass fibers.

[0117] More preferably, the glass fibers have diameter of up to and including 50 pm, more preferably ranging from 5 pm to 20 pm, still more preferably from 8 pm to 15 pmand length equal to or lower than 10 mm, preferably ranging from 0.1 mm to 10 mm, more preferably from 1 mm to 8 mm, still more preferably from 2 mm to 6 mm.

[0118] E-glass fibers are also preferred and generally available as sized fibers, i.e. fibers coated with a coupling agent which increases the compatibility of the fibers with the polymer into which the fibers are dispersed.

[0119] The flame retardant polyolefin composition of the present disclosure comprises one or more flame retardants of the type known in the art, such as halogenated flame retardants, mineral flame retardants (like aluminum hydroxide and magnesium hydroxide), phosphorous-based flame retardants, nitrogen-based flame retardants, borates, antimony oxide and combinations thereof.

[0120] Preferably, the flame retardant e) is a non-halogenated flame retardant optionally selected from phosphorous-based flame retardant materials.

[0121] In embodiments, the flame retardant composition of the instant disclosure further comprises one of more the following components, preferably all (amounts based on the total weight of the flame retardant polyolefin composition):

[0122] f) from 1 to 15 wt.% of a styrene block copolymer; and / or

[0123] g) from 1 to 20 wt.% of a propylene homopolymer; and / or

[0124] h) from 0.1 to 5 wt.% of a coupling agent; and / or

[0125] i) from 0.01 to 5 wt.% of an additive selected from antioxidants, light stabilizers, slipping agents, anti-acids, melt stabilizers, clarifiers, nucleating agents, pigments and combinations thereof.

[0126] Styrene block copolymer f) is a saturated or unsaturated styrene or alphamethylstyrene block copolymer, preferably a styrene block copolymer comprising up to and including 40 wt.% by weight of polystyrene, preferably from 7 to 30 wt.%, more preferably from 12 to 25 wt.%, based on the weight of the styrene block copolymer.

[0127] Preferably, styrene block copolymer f) is selected from the group consisting of: polystyrene-polybutadiene-polystyrene (SBS), polystyrene-poly(ethylene-butylene)-polystyrene (SEBS), polystyrene-poly(ethylene-propylene)-polystyrene (SEPS), polystyrene-polyisoprene-polystyrene (SIS), polystyrene-poly(isoprene-butadiene)-polystyrene (SIBS) and combinations thereof, polystyrene-poly(ethylene-butylene)-polystyrene (SEBS) being particularly preferred.

[0128] The styrene block copolymer f) preferably has one or more of the following properties, preferably all:

[0129] - melt index measured according to ASTM D1238 (230°C, 5 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

[0130] - Shore A value measured according to ASTM 2240 (30 sec.) equal to or lower than 70, preferably ranging from 30 to 70, more preferably from 30 to 60.

[0131] Styrene block copolymers are prepared by ionic polymerization of the relevant monomers and are commercially available e.g. under the tradename of Kraton™ marketed by Kraton Polymers.

[0132] The propylene homopolymer g) is different from propylene homopolymer forming the matrix of the heterophasic propylene polymer a), e.g. different from polymer fraction (A).

[0133] The propylene homopolymer g) is preferably a high melt flow rate propylene homopolymer used to tailor the melt flow rate of the flame retardant polyolefin composition for specific printing conditions. The melt flow rate MFR(g) is preferably equal to or higher than 100 g / 10min, more preferably equal to or greater than 300 g / 10min, still more preferably in the range of from 500 to 2500 g / 10min (ISO 1133-1:2011, 230°C / 2.16 kg).

[0134] Optionally, the propylene homopolymer g) has a molecular weight distribution Mw / Mn equal to or lower than 3, preferably in the range of from 1.2 to 2.7, determined by GPC as described in the examples section.

[0135] Preferably, the propylene homopolymer g) has solubility in xylene equal to or lower than 5 wt.%, more preferably equal to or lower that 3 wt.%, based on the weight of the propylene homopolymer g).

[0136] Propylene homopolymers g) are known in the art and are preferably obtained in a polymerization process using a single site catalyst.

[0137] The coupling agent h) is optionally but preferably comprised in the flame retardant polyolefin composition to increase the compatibility of the reinforcing material,in particular of glass fibers, with the other components. The coupling agent h) is preferably a modified polyolefin functionalized with low molecular weight polar compounds. Preferably, the polyolefin is selected from polyethylenes, polypropylenes and combinations thereof.

[0138] The modified polyolefins are preferably selected from graft copolymers, block copolymers and combinations thereof.

[0139] The modified polyolefins 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.

[0140] Preferably, the coupling agent h) is 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, C1-C10 linear or branched dialkyl fumarates, itaconic anhydride, C1-C10 linear or branched itaconic acid, dialkyl esters, maleic acid, fumaric acid, itaconic acid and combinations thereof.

[0141] In a preferred embodiment, the coupling agent h) is a polyethylene and / or a polypropylene grafted with maleic anhydride (MAH-g-PP and / or MAH-g-PE).

[0142] Preferably, the coupling agent h) is a polyethylene and / or a polypropylene grafted with maleic anhydride, having at least one of the following properties, preferably all:

[0143] - a maleic anhydride graft level equal to or greater than 0.5 wt.%, based on the weight of the coupling agent h), more preferably of from 0.5 wt.% to 3.0 wt.%, still more preferably from 0.75% to 2.0%; and / or

[0144] - a melt flow rate MFR(h) determined according to the method ISO 1133-1 :2011 (190°C, 2.16kg) equal to or greater than 80 g / 10min., preferably ranging from 100 to 200 g / 10min.

[0145] Coupling agents 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 themolten 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.

[0146] 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.

[0147] The flame retardant polyolefin composition optionally further comprises from 0.01 to 5 wt.%, based on the total weight of the flame retardant polyolefin composition, of an additive i) of the type known in the art for use in polyolefin compositions. The additive i) is preferably metered to the flame retardant polyolefin composition as concentrated premix, like dispersed in a polymeric carrier, preferably a propylene homopolymer carrier. In this case, the amount of the polymeric carrier is included in the amount of additive.

[0148] In one embodiment, the flame retardant polyolefin composition of the first aspect consists essentially of components from a) to i) as described in the foregoing.

[0149] The flame retardant polyolefin composition is preferably but not necessarily prepared by blending the component in a mixing apparatus in which the polymeric components are at least partially melt, like in an extruder. After blending, the flame retardant polyolefin compositions is optionally pelletized.

[0150] Preferably, the flame retardant polyolefin composition of the present disclosure has one or more of the following properties, preferably all:

[0151] - melt volume-flow rate in the range of from 1.0 to 20.0 cm3 / 10min, preferably from 3.0 to 10.0 cm3 / 10min (ISO 1133-1:2011, 230°C / 2.16 kg); and / or

[0152] - tensile modulus of from 2000 to 4000 MPa, preferably from 2500 to 3500 MPa (ISO 527-1,-2:2019); and / or

[0153] - tensile stress at yield of from 15 to 45 MPa, preferably from 20 to 40 MPa (ISO 527-1,-2:2019); and / or

[0154] - tensile stress at break of from 25 to 40 MPa, preferably from 27 to 36 MPa (ISO 527-1,-2:2019); and / or

[0155] - Charpy impact resistance at 23°C of from 13 to 35 kJ / m2, preferably from 17 to 25 kJ / m2(ISO 179-1 :2010 1 eA); and / or

[0156] - V-0 burning behavior on 1.60mm plaques and on 3.20mm plaques (DIN EN 60695-11-10, 23°C / 50%LF / 48h).

[0157] The flame retardant polyolefin composition of the present disclosure has a good balance of mechanical properties, like high tensile modulus and high impact resistance, and results in 3D printed articles having low warpage and shrinkage, excellent print quality, like low roughness and good overhangs printability.

[0158] To be use in an additive manufacturing process, the flame retardant polyolefin composition is converted into filaments, beads, pellets or powders.

[0159] Accordingly, the present disclosure also refers to a filament or bead or pellet or powder for additive manufacturing comprising or consisting of the flame retardant polyolefin composition as described in the foregoing.

[0160] In a preferred embodiment, the present disclosure refers to a filament comprising or consisting of the flame retardant polyolefin composition as described in the foregoing having a diameter of 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.

[0161] The filament is preferably prepared by a process comprising the steps of:

[0162] (a) providing the flame retardant polyolefin composition as described in the foregoing or the components from a) to e), and optionally from f) to i);

[0163] (b) extruding the flame retardant polyolefin composition or the components from a) to e), and optionally from f) to i) through a die, preferably a round die, thereby obtaining a filament; and

[0164] (c) cooling the filament, and optionally but preferably rolling up the filament on a spool.

[0165] In an alternative embodiment, the present disclosure refers to beads for additive manufacturing having diameter of from 1 to 5 mm, and comprising or consisting of the flame retardant polyolefin composition described in the foregoing.

[0166] Beads for 3D printing are preferably obtainable by melt blending the component of the flame retardant composition in an extruder, extruding and pelletizing.

[0167] In an alternative embodiment, the present disclosure refers to pellets for additive manufacturing comprising or consisting of the flame retardant polyolefin composition of the first aspect, the pellet having diameter of from 0.5 mm to 5 mm, preferably of from 1.0 mm to 3.0 mm, and length of from 2.0 mm to 10.0 mm, preferably from 4.0 mm to 8.0 mm.

[0168] In a further aspect, the present disclosure provides the use of the flame retardant polyolefin composition as described in the foregoing in an extrusion-based additive manufacturing process.

[0169] In a further aspect, the present disclosure provides an additive manufacturing process comprising selectively depositing a layer of the flame retardant polyolefin composition as described in the foregoing onto a substrate, like a build platform or a 3D printed layer made out of the flame retardant polyolefin composition of the first aspect.

[0170] In a preferred embodiment, the present disclosure refers to an additive manufacturing process (to obtain a flame retardant 3D printed object) comprising the steps of:

[0171] (i) providing a filament or pellet comprising or consisting of the flame retardant polyolefin composition as described in the foregoing;

[0172] (ii) providing a 3D printer with an extruder assembly, a heated extruder nozzle and a build platform;

[0173] (iii) heating the filament or pellet in the extruder assembly, thereby obtaining an at least partially molten flame retardant printing material;

[0174] (iv) extruding the at least partially molten flame retardant printing material through the heated extruder nozzle depositing it layer by layer onto the build platform (thereby building successive printed layers of the 3D printed object).

[0175] Preferably, step (ii) comprises heating the extruder nozzle to a predetermined temperature for at least partially melting the filament or pellets and, optionally, heating the build platform to enhance adhesion. Optionally, step (ii) further comprises positioning the filament spool in the filament holder of the 3D printer.

[0176] In step (iv) the layers of molten polymer material are deposited onto the built platform based on a digital 3D model of the object. Optionally, step (iv) comprises dynamically adjusting printing parameters, including layer height, print speed, and nozzle temperature, based on the specific requirements of the 3D model.

[0177] Step (iv) comprises allowing each printed layer to cool and solidify before proceeding to printing the next layer.

[0178] Optionally but preferably, the additive manufacturing process further comprises a step (v) of removing the build platform from the 3D printed object and optionally mechanically finishing the 3D printed object, like removing scraps and / or smoothing.

[0179] Powders or beads for 3D printing comprising or consisting of the flame retardant polyolefin composition described in the foregoing can be printed using a Selective Laser Sintering process.

[0180] In a further aspect, the present disclosure refers to a flame retardant 3D printed article comprising or consisting of the flame retardant polyolefin composition as described in the foregoing.

[0181] In a preferred embodiment, the 3D printed object is obtained by the additive manufacturing process described above making use of a filament or pellets as feedstocks.

[0182] The 3D printed object shows good surface quality even at the overhangs, such as low roughness, no drooping, sagging or curling. It shows a good balance of mechanical properties, dimensional stability and good layer adhesion.EXAMPLES

[0183] The following examples are given to illustrate the present invention without limiting purpose.

[0184] CHARACTERIZATION METHODS: the following methods are used to determine the properties indicated in the description, claims and examples.

[0185] Melt Flow Rate: Determined according to the method ISO 1133-1:2011 (230°C / 2.16 kg).

[0186] 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 is lowered 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 (S1) 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.

[0187] 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 1, 1,2,2-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 ofmonomer sequence distribution in ethylene-propylene copolymers prepared with 5-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 = 100 Tp5 / S EPE = 100 T55 / SPEP = 100 Spp / S PEE= 100 Sp5 / S EEE = 100 (0.25 SyQ+0.5 S55) / S S = Tpp + Tp5 + T55 + Spp + Sp5 + 0.25 Sy5 + 0.5 S55

[0188] The molar percentage of ethylene content was evaluated using the following equation:E% mol = 100 * [PEP+PEE+EEE]

[0189] The weight percentage of ethylene content was evaluated using the following equation:100 * E% mol * MWEE% wt. = >E% mol * MWE + P% mol * MWp

[0190] where P% mol is the molar percentage of propylene content, while MWE and MWp are the molecular weights of ethylene and propylene, respectively.

[0191] 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 S55 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 1, 1,2,2-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 ethylene-propylene copolymers prepared with 5-titaniumtrichloride- diethylaluminum chloride” M. Kakugo, Y. Naito, K. Mizunuma and T. Miyatake, Macromolecules, 1982, 15, 1150) using the following equations:PPP = 100 lw / S PPE = 100 l6 / S EPE = 100 l5 / SBBB = 100 l3 / S BBE = 100 l2 / S EBE = 100 ln / SXEX = 100 I12 / S XEE = 100 (h+l4) / S EEE = 100 (0.5l9+0.25(l7+l8)) / SS = 11 +I2+I3+I4+I5+I6+O.25I7+O.2518+O.5I9+11 o+l 11 +l 12

[0192] Wherein X is propylene (P) or butene-1 (B) and h to I12 are the areas of the corresponding carbon atoms as reported in the following table:

[0193] 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]

[0194] 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)

[0195] 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.

[0196] Molecular weight distribution Mw / Mn: The determination of the Mn, Mw, and Mw / Mn was carried out using a Waters GPCV 2000 apparatus, which was equipped with a column set of four PLgel Olexis mixed-gel (Polymer Laboratories) having a particle size of 13 pm and an IR4 infrared detector (PolymerChar). The dimensions of the columns were 300x7.5 mm. The mobile phase used was vacuum distilled 1-2-4-trichlorobenzene (TCB) and its flow rate was kept at 1.0 ml / min. The sample solution was prepared by heating the sample under stirring at 150°C in TCB for one to two hours. Solution concentration was 1 mg / ml in TCB. 0.1 g / l of 2,6-diterbuthyl-p-chresole were added to prevent degradation. For GPC calculation, a universal calibration curve was obtained using 10 polystyrene (PS) standard samples supplied by Polymer Laboratories (peak molecular weights ranging from 580 to 8500000). A third order polynomial fit was used for interpolating the experimental data and obtaining the relevant calibration curve. Data acquisition and processing was done using Empower (Waters). The Mark-Houwink relationship was used to determine the molecular weight distribution and the relevant average molecular weights: the K values were KPS = 1.21x1 O’4dL / g and KPB = 1.78x10’4dL / g for PS and PB respectively, while the Mark-Houwink exponents a = 0.706 for PS and a = 0.725 for PB were used.

[0197] Vicat softening temperature: determined according to ISO 306:2022, A50.

[0198] Melting temperature: determined according to ISO 11357-3:2018, at scanning rate of20°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.

[0199] Seal Initiation Temperature: Film strips 6 cm wide and 35 cm length are cut from the center of a BOPP prepared as described below and superimposed. The superimposed specimens are sealed along one of the 6 cm sides with a RDM HSE-3 heat sealer equipped with metal jaws with uncoated flat surface. Sealing time is 5 seconds at a pressure of 0.14 MPa (20 psi). The starting sealing temperature lower (ca. 10°C) than the expected sealing temperature of the test specimen. After at least 10 minutes ofconditioning at 23°C and 50 %RH, 6 specimens are cut from the sealed strips, 15 mm wide and long enough to be clamped in the tensile tester grips. The seal strength is measured (Instron 5565A) with a load cell capacity of 100 N, cross speed of 100 mm / min and grip distance of 50 mm. Measurements are repeated 6 times for each sealing temperature, and the results is expressed as the average of maximum seal strength (N).

[0200] The test is than repeated by changing the heat sealer temperature as follows:

[0201] If seal strength <1.5 N then increase the temperature

[0202] If seal strength >1.5 N then decrease the temperature

[0203] Temperature variation must be adjusted stepwise, if seal strength is close to target select steps of 1 °C if the strength is far from target select steps of 2°C.

[0204] The seal strength is measured at different sealing temperatures until the lowest temperature at which a seal strength equal to or higher than 1.5 N is achieved. This is defines as the Sealing Initiation Temperature (SIT).

[0205] Preparation of BOPP film test specimens. Films with thickness of 50 pm are prepared by extruding each test composition in a single screw Collin extruder (length / diameter ratio of screw 1:25) at a film drawing speed of 7 m / min and a melt temperature of 210-250°C. Each film is superimposed on a 1000pm thick film of a propylene homopolymer having a xylene insoluble fraction of 97 wt.% and a MFR (ISO1133-1:2011, 230°C / 2.16kg) of 2.0 g / 10 min. The superimposed films are bonded to each other in a plat press at 200°C under a 35 kg x cm2load, which is maintained for 5 minutes. The resulting laminates are simultaneously stretched longitudinally and transversally, i.e. biaxially, by a factor 7 with a Karo 4 Brueckenerfilm stretcher at 160°C, thus obtaining a 20pm thick BOPP film (18pm homopolymer + 2pm test composition).

[0206] Density: determined according to ISO 1183-1 / A:2019 at 23°C.

[0207] Tensile properties: determined according to ISO 527-1,-2:2019 on injection molded specimens Type A1 according to ISO 20753:2018.

[0208] Charpy impact strength: determined according to ISO 179-1:2010 1eA on injection molded specimens Type B1 according to ISO 20753:2018.

[0209] Burning behavior: determined according to DIN EN 60695-11-10, 23°C / 50%LF / 48h.

[0210] Warpage: measured on a 3D printed frame having geometry according to FIG.2. Warpage values have been established by placing the frame on a flat surface and measuring the height of the four corner positions with respect to the surface itself. Three specimens were printed and measured for each polyolefin composition.

[0211] RAW MATERIALS

[0212] HECO: heterophasic propylene copolymer comprising, based on the weight of the heterophasic propylene copolymer:

[0213] - 56.5 wt.% of a propylene homopolymer (A) having solubility in xylene at 25°C of 3 wt.%, based on the weight of the homopolymer, and a MFR of 70 g / 10min (ISO 1133-1:2011, 230°C / 2.16 kg);

[0214] - 43.5 wt% of a copolymer fraction (B) containing 58 wt.% of polymerized units deriving from ethylene, based on the weight of the fraction (B), the fraction (B) comprising an ethylene / butene-1 copolymer (B1) containing 72 wt.% of polymerized units deriving from ethylene, based on the weight of the copolymer (B1), and a propylene / ethylene copolymer (B2) in a weight ratio (B1) / (B2) of 1.12:1.

[0215] Properties of the heterophasic propylene copolymer are reported in Table 1.

[0216] The polymer was obtained as described in Example 1 of W003 / 076511.

[0217] TERPO: is a propylene / ethylene / butene-1 terpolymer containing 3.2 wt.% of polymerized units derived from ethylene and 6.0 wt.% of polymerized units derived from butene-1. The terpolymer was prepared as described in Examples 4-6 of W003 / 031514A1 by properly adjusting the polymerization conditions.

[0218] The properties of the obtained material are reported in Table 1.Table 1<

[0219] Engage 8200: an ethylene / octene-1 copolymer from Dow with density of 0.870 g / cm3(ASTM D792), melt index of 5.0 g / 10 min (ASTM D1238, 190°C / 2.16Kg) and Shore A of 66 (ASTM D2240).

[0220] Engage 7467: an ethylene / butene-1 copolymer from Dow with density of 0.862 g / cm3(ASTM D792), melt index of 1.2 g / 10 min (ASTM D1238, 190°C / 2.16Kg) and Shore A of 52 (ASTM D2240).

[0221] Metocene MF650Y: a propylene homopolymer from LyondellBasell, having a melt flow rate of 1800 g / 10 min. (ISO1133; 230°C / 2.16Kg).

[0222] Kraton™ G1657: from Kraton Corp., a linear triblock copolymer based on styrene and ethylene / butylene with a polystyrene content of 13 wt.%, having melt index (ASTM D1238; 230°C, 5 Kg) of 22 g / Wmin.

[0223] DS2200-10P: chopped E-glass fibers from 3B Fibreglass Company having fiber diameter of 10 pm and chopped strands length of 4mm.

[0224] Coupling agent: maleic anhydride modified propylene homopolymer with a maleic anhydride content (FTIR) of 1 wt.% and a melt flow rate (ASTM D1238) of ca. 170 g / 10min.

[0225] ADK STAB FP-2100JC: nitrogen / phosphorous-based, halogen-free flame retardant by Adeka.

[0226] AP: additive package securing the addition of, based on the total weight of the flame retardant polyolefin composition: 0.20 wt.% MgO, 0.10 wt.% of a low molecular weight hindered amine light stabilizer, 0.20 wt.% of a slip agent, 0.20 wt.% processing stabilizer, 0.30 wt.% of antioxidant and 2.00 wt.% of a propylene homopolymer with MFR 10 g / 10min as carrier resin.

[0227] Examples E1-E2 and Comparative Example CE3

[0228] The compositions of E1-E2 and CE3 were obtained by compounding the components in a twin-screw extruder LAB LINE model ZSK 26 MC18 from Coperion operated in the following conditions:

[0229] - feeding zone temperature: 160°C;

[0230] - zone 3-12 temperature: 230°C;

[0231] - screw speed: 600rpm;

[0232] - melt temperature: 250-260°C;

[0233] - throughput: ca. 65 kg / h;

[0234] - vacuum pressure: min. 600bar;

[0235] - additives added by side feeding.

[0236] Mechanical properties of the compositions were measured on injection molded specimens Type B2 according to ISO 20753-A1:2018-10 and are reported in Table 2.

[0237] Filaments of diameter 2.85±0.02mm were produced from the flame retardant 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: 210°C- screw speed: 108-112 rpm- melt pressure: 30-60 bar- throughput: 1.2 kg / h- haul-off speed: 7-17 m / min

[0238] The extruded polymer strand was withdrawn, water cooled and rolled up on a spool. The filaments were fed to a UltiMaker 53D printer, and 3D printed test specimens were produced having shape according to ISO 20753:2018, Type A1 or Bx, andorientation illustrated in FIG.1. Printing conditions are illustrated in Table 3 below. Test results on the 3D printed specimen are reported in Table 4.Table 2

[0239] The test specimens of examples E1 and E2 were self-extinguishing, i.e. the burning rate was not measurable.Table 3Table 4

[0240] The compositions of examples E1 and E2 have an improved mechanical property profile and resulted in 3D printed items having superior surface quality, like lower surface roughness, if compared with the composition of CE3.

[0241] Compositions of E1 and E2 also have good printing quality, like stable overhangs and no warpage of the comers was measurable.

[0242] Comparative example CE4

[0243] In Comparative Example CE4 a composition according to WO2021 / 069242 was tested for burning behavior. The composition was classified in HB category for burning behavior, with a burning rate of 66 mm / min for a 1 ,70mm plaque and of 44 mm / min for a 3.00mm plaque.

Claims

CLAIMSWhat is claimed is:

1. A flame retardant polyolefin composition for additive manufacturing comprising, based on the total weight of the flame retardant polyolefin composition:a) from 5 to 30 wt.% of an heterophasic propylene copolymer;b) from 1 to 25 wt.% of a propylene / ethylene / C4-C10alpha-olefin terpolymer; c) from 1 to 20 wt.% of an elastomeric copolymer of ethylene with propylene or a C4-C10alpha-olefin;d) from 1 to 25 wt.% of a reinforcing material; ande) at least 15 wt.% of a flame retardant material.

2. The flame retardant polyolefin composition of claim 1 comprising, based on the total weight of the flame retardant polyolefin composition:a) from 10 to 20 wt.% of an heterophasic propylene copolymer; and / orb) from 5 to 20 wt% of a propylene / ethylene / C4-C10alpha-olefin terpolymer; and / or c) from 5 to 15 wt.% of an elastomeric copolymer of ethylene with propylene or a C3-C10alpha-olefin; and / ord) from 10 to 20 wt.% of a reinforcing material; and / ore) from 20 to 40 wt.% of a flame retardant material.

3. The flame retardant polyolefin composition of claim 1 or 2, wherein the heterophasic propylene copolymer a) has one or more of the following properties:a.) Vicat softening temperature in the range from 110° to 130°C (A50, ISO 306:2022); and / ora.ii) melting temperature in the range of from 135°C to 165°C (ISO 11357-3:2018); and / ora.iii) melt flow rate MFR(a) in the range of from 2 to 50 g / 10min, preferably from 5 to 25 g / 1 Omin (ISO 1133-1 :2011 , 230°C / 2.16 kg); and / ora.iv). tensile modulus in the range of from 400 to 1200 MPa, preferably from 600 to 1000 MPa (ISO 527-1,-2:2019); and / ora.v) Charpy impact strength at 23°C in the range of from 20 to 70 kJ / m2, preferably from 35 to 60 kJ / m2 (ISO 179-1:2010 1eA).

4. The flame retardant polyolefin composition of any one of the previous claims, wherein the heterophasic propylene copolymer a) comprises, based on the weight of the heterophasic propylene copolymer a):- from 15 to 70 wt.% of a polymer fraction (A) comprising a propylene homopolymer or a copolymer of propylene with ethylene or a C4-C10alpha-olefin containing up to 10 wt.%, based on the weight of the fraction (A), of polymerized units deriving from ethylene or the alpha-olefin, the fraction (A) having solubility in xylene at 25°C XS(A) lower than 10 wt.%, based on the weight of fraction (A), wherein the xylene soluble fraction at 25°C is determined according to the method described in the examples section; and-from 30 to 85 wt.% of a copolymer fraction (B) comprising a copolymer of ethylene with propylene or a C4-C10alpha-olefin, the copolymer fraction (B) containing from 20 to 75 wt.%, preferably from 35 to 70 wt.%, of polymerized units derived from ethylene, based on the weight of the copolymer fraction (B), wherein the copolymer fraction (B) is different from component c).

5. The flame retardant polyolefin composition of any one of the previous claims, wherein the heterophasic propylene copolymer a) comprises, based on the weight of the heterophasic propylene copolymer a):- from 45 to 65 wt.%, preferably from 50 to 60 wt.%, of a fraction (A) comprising a propylene homopolymer or a copolymer of propylene with ethylene or a C4- C10alpha-olefin containing up to 10 wt.%, based on the weight of the fraction (A), of polymerized units deriving from ethylene or the alpha-olefin, the fraction (A) having solubility in xylene at25°C XS(A) lower than 10 wt.%, based on the weight of fraction (A); and- from 35 to 55 wt.%, preferably from 40 to 50 wt.%, of a copolymer fraction (B) comprising a copolymer of ethylene with a C4-C10alpha-olefin (B1) and anethylene / propylene copolymer (B2), wherein the weight ratio (B1) / (B2) is from 2:1 to 1:2 and wherein the copolymer fraction (B) contains from from 35 to 75 wt.%, preferably from 45 to 70 wt.%, of polymerized units derived from ethylene, based on the weight of the copolymer fraction (B).

6. The flame retardant polyolefin composition of claim 4 or 5, wherein component (A) comprises a propylene homopolymer and has solubility in xylene at 25°C XS(A) lower than 5 wt.%, preferably equal to or lower than 3 wt.%, based on the weight of fraction (A).

7. The flame retardant polyolefin composition of any one of claims from 4 to 6, wherein polymer fraction (A) has melt flow rate MFR(A) in the range of from 30 to 100 g / Wmin, preferably from 50 to 80 g / 10min (ISO 1133-1:2011 (230°C / 2.16 kg).

8. The flame retardant polyolefin composition of any one of claims from 5 to 7, wherein copolymer (B1) is an ethylene / butene-1 copolymer, preferably comprising from 60 to 80 wt.% of polymerized units deriving from ethylene, based on the weight of copolymer (B1).

9. The flame retardant polyolefin composition of any one of claims from 5 to 8, wherein the weight ratio (B1) / (B2) is in the range from 1.5:1 to 1:1.

10. The flame retardant polyolefin composition of any one of the previous claims, wherein the heterophasic propylene copolymer a) has:- xylene soluble fraction at 25°C XS(a) in the range of from 25 to 50 wt.%, preferably from 30 to 40 wt.%, based on the weight of the heterophasic propylene copolymer a); and / or- intrinsic viscosity of the fraction soluble in xylene at 25°C XSIV(a) of the heterophasic propylene copolymer a) is in the range of from 1.5 to 3.5 dl / g, whereinthe intrinsic viscosity is determined according to the method described in the examples section.

11. The flame retardant polyolefin composition of any one of the previous claims, wherein the propylene / ethylene / C4-C10alpha-olefin terpolymer b) is selected from: b1) propylene / ethylene / butene-1 terpolymers containing from 0.5 to 7.0 wt.% of polymerized units derived from ethylene and from 2.0 to 17.0 wt.% of polymerized units derived from butene-1, based on the total weight of the terpolymer b1 ), b2) propylene / ethylene / hexene-1 terpolymers containing from 0.5 to 5.0 wt.% of polymerized units derived from ethylene and from 1.0 to 12.0 wt.% of polymerized units derived from hexene-1 , based on the total weight of the terpolymer b2), and b3) combinations thereof.

12. The flame retardant polyolefin composition of any one of the previous claims, wherein the propylene / ethylene / alpha-olefin terpolymer b) has one or more of the following properties:b.i) melt flow rate MFR(b) in the range of from 1 to 20 g / 10min, preferably from 3 to 10 g / 1 Omin (ISO 1133-1 :2011 , 230°C / 2.16 kg); and / orb.ii) xylene soluble fraction at25°C in the range of from 4 to 25 wt.%, preferably from 6 to 15 wt.%, based on the weight of the terpolymer b), wherein the xylene soluble fraction is determined according to the method described in examples section; and / orb.iii) Vicat softening temperature in the range from 105° to 120°C (A50, ISO 306:2022); and / orb.iv) melting temperature in the range of from 125° to 143°C (ISO 11357-3:2018); and / orb.v) Seal Initiation Temperature in the range of from 100° to 115°C, determined according to the method described in the example section.

13. The flame retardant polyolefin composition of any one of the previous claims, wherein in ethylene component c) the alpha olefin is selected from butene-1, hexene-1 and octene-1.

14. The flame retardant polyolefin composition of any one of the previous claims, wherein ethylene component c) is an ethylene / octene-1 copolymer.

15. The flame retardant polyolefin composition of any one of the previous claims, wherein the ethylene copolymer c) contains at most 80 wt.% of polymerized units derived from ethylene, preferably from 50 to 80 wt.% of units derived from ethylene, based on the weight of the ethylene copolymer c).

16. The flame retardant polyolefin composition of any one of the previous claims, wherein the elastomeric ethylene / alpha-olefin copolymer c) has one or more of the following properties:c.i) density in the range of from 0.855 to 0.910 g / cm3, preferably from 0.860 to 0.880 g / cm3(ASTM D792); and / orc.ii) melt index in the range of from 0.1 to 30 g / 10min, preferably from 3 to 15 g / 10min (ASTM D1238, 2.16Kg at 190°C); and / orc.iii) Shore A value of from 50 to 90, preferably from 55 to 75 (ASTM D2240).

17. The flame retardant polyolefin composition of any one of the previous claims, wherein the reinforcing material d) is glass fibers.

18. The flame retardant polyolefin composition of claim 17, wherein the glass fibers have diameter of up to and including 50 pm, preferably ranging from 5 pm to 20 pm, more preferably from 8 pm to 15 pm and length equal to or lower than 10 mm, preferably ranging from 0.1 mm to 10 mm, more preferably from 1 mm to 8 mm, still more preferably from 2 mm to 6 mm.

19. The flame retardant polyolefin composition of any one of the previous claims, further comprising one or more of the following components, based on the total weight of the flame retardant polyolefin composition:f) from 1 to 15 wt.% of a styrene block copolymer; and / org) from 1 to 20 wt.% of a propylene homopolymer; and / orh) from 0.1 to 5 wt.% of a coupling agent; and / ori) from 0.01 to 5 wt.% of an additive selected from antioxidants, light stabilizers, slipping agents, anti-acids, melt stabilizers, clarifiers, nucleating agents, pigments and combinations thereof.

20. The flame retardant polyolefin composition of any one of the previous claims having one or more of the following properties:- melt volume-flow rate in the range of from 1.0 to 20.0 cm3 / 10min, preferably from 3.0 to 10.0 cm3 / 10min (ISO 1133-1:2011, 230°C / 2.16 kg); and / or- tensile modulus of from 2000 to 4000 MPa, preferably from 2500 to 3500 MPa (ISO 527-1,-2:2019); and / or- tensile stress at yield of from 15 to 45 MPa, preferably from 20 to 40 MPa (ISO 527-1,-2:2019); and / or- tensile stress at break of from 25 to 40 MPa, preferably from 27 to 36 MPa (ISO 527-1,-2:2019); and / or- Charpy impact resistance at 23°C of from 13 to 35 kJ / m2, preferably from 17 to 25 kJ / m2(ISO 179-1:2010 1eA); and / or- V-0 burning behavior on 1.60mm plaques and on 3.20mm plaques (DIN EN 60695-11-10, 23°C / 50%LF / 48h).

21. A filament or bead or pellet or powder for additive manufacturing comprising the flame retardant polyolefin composition of any one of claims from 1 to 20.

22. An additive manufacturing process comprising the steps of:(i) providing a filament or pellet comprising the flame retardant polyolefin composition of to any one of claims from 1 to 20;(ii) providing a 3D printer with an extruder assembly, a heated extruder nozzle and a build platform;(iii) heating the filament or pellet in the extruder assembly, thereby obtaining an at least partially molten flame retardant printing material; and(iv) extruding the at least partially molten flame retardant printing material through the heated extruder nozzle depositing it layer by layer onto the build platform.

23. The additive manufacturing process according to claim 22 further comprising a step (v) of removing the build platform from the 3D printed object and optionally mechanically finishing the 3D printed object.

24. A flame retardant 3D printed article comprising the flame retardant polyolefin composition of any one of claims from 1 to 20.

Images