WO2021195070A1 - Processes for making 3-d objects from blends of polypropylene and semi-amorphous polymers - Google Patents

Abstract

This invention relates to a process for making a three-dimensional object using an additive manufacturing process. A blend can be prepared that can include polypropylene and a semi- amorphous polymer, the semi-amorphous polymer having at least 60 wt% propylene-derived units and from 5 to 25 wt% ethylene-derived units, based on a total weight of the semi-amorphous polymer, and having a heat of fusion of less than about 80 J/g. The blend can be extruded to make a filament. The filament can be inserted into an additive manufacturing apparatus that can have a nozzle. The filament can be heated. A fluid bead of the filament can be dispensed out of the nozzle to manufacture a three-dimensional object.

Description

Processes for Making 3-D Objects from Blends of Polypropylene and Semi-Amorphous Polymers

INVENTORS: Ru Xie, Ying Ying Sun

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of and priority to US Provisional Application No. 63/000,289, filed March 26, 2020, the disclosure of which is incorporated herein by reference.

FIELD

[0002] This invention relates to additive manufacturing. More particularly, this invention relates to using an additive manufacturing process such as fused filament fabrication to make 3-D objects from blends of polypropylene and semi-amorphous polymers.

BACKGROUND

[0003] Traditional manufacturing processes, known as “subtractive manufacturing”, use material that are carved or shaped into a desired product by parts of the material being removed in a variety of ways. Additive manufacturing, also known as 3-D printing, was created to do the exact opposite. In additive manufacturing, a 3-D object is made by successively adding material layer-by-layer to produce a product having a predetermined geometry. The design of the 3-D object is typically made and controlled by a computer. A computer-aided design (CAD) software program is typically used to relay messages to a 3-D printer so that it “prints” in the desired shape. [0004] The benefits of this more modem technology are that new products can be made with massive customization, improved material utilization, and a greater range of designs. Designs that cannot be manufactured in one entire piece with traditional means can easily be achieved using additive manufacturing. For example, shapes with a scooped out or hollow center can be produced as a single piece, without the need to weld or attach individual components together. Due to such benefits, additive manufacturing has found application in, for example, the plastics, construction, and automotive industries.

[0005] Because of its relative simplicity, the additive manufacturing process known as fused filament fabrication (FFF) is widely used for the production of plastics. In FFF, filaments of a thermoplastic are melted or extruded through a hot end of a nozzle and deposited as layers that harden and build up to form the desired 3-D object. Currently, two commercially available thennoplastics (i.e., acrylonitrile-butadiene-styrene (ABS) and polylactic acid (PLA)) and three engineering thermoplastics ( i.e ., polycarbonate (PC), poly(ether imide) (PEI), and polyether ether ketone (PEEK)) are primarily used for FFF due to their availability and ability to form products with adequate mechanical properties and dimensional accuracy. One drawback for using such specialty polymers is their high cost.

[0006] Ideally, low cost commodity thermoplastics could be used in additive manufacturing via FFF. However, there are challenges that arise from the nature of the FFF process with using commodity thermoplastics, particularly polyolefins. For example, degradation of mechanical properties of the final product can occur as a result of internal interfaces between the layers of deposited polymer. Also, the final product can experience warpage due to crystallization induced stresses caused by thermal expansion.

[0007] A need therefore exists for a thermoplastic that is suitable for use in additive manufacturing, particularly FFF, and can be used to produce products having adequate mechanical properties and less warpage.

[0008] Additional references of interest may include: WO 2019/0197582A1, CN103980396A, JP2019203228 A, CN103980395B, and JP2018035461 A.

SUMMARY OF INVENTION

[0009] A process for making an object using an additive manufacturing process is provided herein. In some examples, a blend can be prepared that can include polypropylene and a semi- amorphous polymer having at least 60 wt% propylene-derived units and from 5 to 25 wt% ethylene-derived units, based on a total weight of the semi-amorphous polymer, and having a heat of fusion of less than about 80 J/g. The blend can be extruded to make a filament. The filament can be inserted into an additive manufacturing apparatus that can have a nozzle. The filament can be heated. A fluid bead of the filament can be dispensed out of the nozzle to manufacture a three- dimensional object.

[0010] A process for making a filament is also provided herein. In some examples, a blend can be prepared that can include polypropylene and a semi-amorphous polymer. The semi- amorphous polymer can have at least 60 wt% propylene-derived units and from 5 to 25 wt% ethylene-derived units, based on a total weight of the semi-amorphous polymer, and having a heat of fusion of less than about 80 J/g. The blend can be extruded to make a filament where the filament has a diameter from 0.01 mm to 1 m. The filament can be collected on a spool. [0011] A filament is also provided herein. The filament can include a blend of polypropylene and a semi-amorphous polymer. The semi-amorphous polymer can have at least 60 wt% propylene-derived units and from 5 to 25 wt% ethylene-derived units, based on a total weight of the semi-amorphous polymer, and having a heat of fusion of less than about 80 J/g. The filament can have a diameter from about 1 mm to about 3 mm.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0012] It is to be understood that the following disclosure describes several exemplary embodiments for implementing different features, structures, and/or functions of the invention. Exemplary embodiments of components, arrangements, and configurations are described below to simplify the present disclosure; however, these exemplary embodiments are provided merely as examples and are not intended to limit the scope of the invention. Additionally, the present disclosure may repeat reference numerals and/or letters in the various exemplary embodiments and across the Figures provided herein. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various exemplary embodiments and/or configurations discussed in the Figures. Moreover, the exemplary embodiments presented below can be combined in any combination of ways, i.e., any element from one exemplary embodiment can be used in any other exemplary embodiment, without departing from the scope of the disclosure.

[0013] For purposes of this invention and the claims thereto, a “catalyst system” is a combination of at least two catalyst compounds, an activator, and a support material. The catalyst systems may further comprise one or more additional catalyst compounds. The terms “mixed catalyst system”, “dual catalyst system”, “mixed catalyst”, and “supported catalyst system” may be used interchangeably herein with “catalyst system.” For the purposes of this invention and the claims thereto, when catalyst systems are described as comprising neutral stable forms of the components, it is well understood by one of ordinary skill in the art, that the ionic form of the component is the form that reacts with the monomers to produce polymers.

[0014] The term “complex” is used to describe molecules in which an ancillary ligand is coordinated to a central transition metal atom. The ligand is bulky and stably bonded to the transition metal so as to maintain its influence during use of the catalyst, such as polymerization. The ligand may be coordinated to the transition metal by covalent bond and/or electron donation coordination or intermediate bonds. The transition metal complexes are generally subjected to activation to perform their polymerization function using an activator which is believed to create a cation as a result of the removal of an anionic group, often referred to as a leaving group, from the transition metal. "Complex," as used herein, is also often referred to as "catalyst precursor", "pre-catalyst", "catalyst", "catalyst compound", "metal compound", "transition metal compound", or "transition metal complex". These words are used interchangeably. “Activator” and “cocatalyst” are also used interchangeably.

[0015] The terms "hydrocarbyl radical," "hydrocarbyl" and "hydrocarbyl group" are used interchangeably throughout this document. Likewise the terms "group", "radical", and "substituent" are also used interchangeably in this document. For purposes of this invention, "hydrocarbyl radical" is defined to be Ci-Cioo radicals, that may be linear, branched, or cyclic, and when cyclic, aromatic or non-aromatic.

[0016] For purposes of this invention and claims thereto, unless otherwise indicated, the term “substituted” means that a hydrogen group has been replaced with a heteroatom, or a heteroatom containing group. For example, substituted hydrocarbyl radicals are radicals in which at least one hydrogen atom of the hydrocarbyl radical has been substituted with at least one functional group such as Cl, Br, F, I, NR*₂, OR*, SeR*, TeR*, PR*₂, AsR*₂, SbR*₂, SR*, BR*₂, SiR*₃, GeR*₃, SnR*₃, PbR*₃ and the like (where R* is H or a Ci to C₂o hydrocarbyl group), or where at least one heteroatom has been inserted within a hydrocarbyl ring.

[0017] The term "ring atom" means an atom that is part of a cyclic ring structure. By this definition, a benzyl group has six ring atoms and tetrahydrofuran has 5 ring atoms.

[0018] A "ring carbon atom" is a carbon atom that is part of a cyclic ring structure. By this definition, a benzyl group has six ring carbon atoms and para-methylstyrene also has six ring carbon atoms.

[0019] The term "aryl" or "aryl group" means a six carbon aromatic ring and the substituted variants thereof, including but not limited to, phenyl, 2-methyl -phenyl, xylyl, 4-bromo-xylyl. Likewise, heteroaryl means an aryl group where a ring carbon atom (or two or three ring carbon atoms) has been replaced with a heteroatom, preferably, N, O, or S.

[0020] A "heterocyclic ring" is a ring having a heteroatom in the ring structure as opposed to a heteroatom substituted ring where a hydrogen on a ring atom is replaced with a heteroatom. For example, tetrahydrofuran is a heterocyclic ring and 4-N,N-dimethylamino-phenyl is a heteroatom substituted ring. [0021] As used herein the term "aromatic" also refers to pseudoaromatic heterocycles which are heterocyclic substituents that have similar properties and structures (nearly planar) to aromatic heterocyclic ligands, but are not by definition aromatic; likewise, the term aromatic also refers to substituted aromatics.

[0022] The term "continuous" means a system that operates without interruption or cessation. For example, a continuous process to produce a polymer would be one where the reactants are continually introduced into one or more reactors and polymer product is continually withdrawn. [0023] As used herein, the numbering scheme for the Periodic Table groups is the new notation as set out in Chemical and Engineering News, v.63(5), 27, (1985).

[0024] An "olefin", is a linear, branched, or cyclic compound of carbon and hydrogen having at least one double bond. For purposes of this specification and the claims appended thereto, when a polymer or copolymer is referred to as comprising an olefin, the olefin present in such polymer or copolymer is the polymerized form of the olefin. For example, when a copolymer is said to have an "ethylene" content of 35 wt%to 55 wt%, it is understood that the mer unit in the copolymer is derived from ethylene in the polymerization reaction and said derived units are present at 35 wt% to 55 wt%, based upon the weight of the copolymer. A “polymer” has two or more of the same or different mer units. A “homopolymer” is a polymer having mer units that are the same. A “copolymer” is a polymer having two or more mer units that are different from each other. “Different” as used to refer to mer units indicates that the mer units differ from each other by at least one atom or are different isomerically. Accordingly, the definition of copolymer, as used herein, includes terpolymers and the like. An "ethylene polymer" or "ethylene copolymer" is a polymer or copolymer comprising at least 50 mol% ethylene derived units, a "propylene polymer" or "propylene copolymer" is a polymer or copolymer comprising at least 50 mol% propylene derived units, and so on.

[0025] As used herein, M_n is number average molecular weight, M_w is weight average molecular weight, and M_z is z average molecular weight, wt% is weight percent, and mol% is mole percent. Molecular weight distribution (MWD), also referred to as polydispersity index (PDI), is defined to be Mw divided by Mn. Unless otherwise noted, all molecular weights (e.g., Mw, Mn, Mz) are reported in units of g/mol. The following abbreviations may be used herein: Me is methyl, Et is ethyl, t-Bu and ^lBu are tertiary butyl, iPr and 'Pr are isopropyl, Cy is cyclohexyl, THF (also referred to as thf) is tetrahydrofuran, Bn is benzyl, Ph is phenyl, Cp is cyclopentadienyl, Cp* is pentamethyl cyclopentadienyl, Ind is indenyl, Flu is fluorenyl, and MAO is methylalumoxane. [0026] As used herein, the term "polypropylene", "propylene polymer," or "PP" refers to homopolymers, copolymers, terpolymers, and interpolymers, comprising from 50 to 100 weight % of propylene.

[0027] As used herein "semi-crystalline polymer" is defined to be an olefin polymer having a melting point (Tm) of 100°C or more (as measured by DSC-second melt, described below). As used herein a "semi-amorphous polymer" is defined to be an olefin polymer having a heat of fusion of between 4 and 70 J/g (as determined by DSC, described below). Melting point (Tm), peak crystallization temperature (Tc), heat of fusion (Hf) and percent crystallinity are determined using the following procedure according to ASTM E 794-85. Differential scanning calorimetric (DSC) data is obtained using a TA Instruments model 2910 machine or a Perkin-Elmer DSC 7 machine. In the event that the TA Instruments 2910 machine and the Perkin-Elmer DSC-7 machine produce different DSC data, the data from the TA Instruments model 2910 shall be used. Samples weighing approximately 5-10 mg are sealed in aluminum sample pans. The DSC data is recorded by first cooling the sample to -50°C and then gradually heating it to 200°C at a rate of 10°C/minute. The sample is kept at 200°C for 5 minutes before a second cooling-heating cycle is applied. Both the first and second cycle thermal events are recorded. Areas under the melting curves are measured and used to determine the heat of fusion and the degree of crystallinity. The percent crystallinity (X%) is calculated using the formula, X% = [area under the curve (Joules/gram) / B (Joules/gram)] * 100, where B is the heat of fusion for the homopolymer of the major monomer component. These values for B are to be obtained from the Polymer Handbook , Fourth Edition, published by John Wiley and Sons, New York 1999. A value of 189 J/g (B) is used as the heat of fusion for 100% crystalline polypropylene. For the semi-crystalline polymers, having appreciable crystallinity, the melting temperature is typically measured and reported during the second heating cycle (or second melt). For the semi-amorphous polymers, having comparatively low levels of crystallinity, the melting temperature is typically measured and reported during the first heating cycle. Prior to the DSC measurement, the sample is aged (typically by holding it at ambient temperature for a period up to about 5 days) or annealed to maximize the level of crystallinity. [0028] This invention relates to a novel 3-D printing material which can be or include a blend of one or more polypropylenes and one or more semi-amorphous polymers, where the one or more semi-amorphous polymers can include at least about 60 wt% propylene-derived units and from about 5 to about 25 wt% ethylene-derived units, based on total weight of the one or more semi- amorphous polymers, and the one or more semi-amorphous polymers can have a heat of fusion of less than about 80 j/g.

[0029] It has been surprising and unexpectedly discovered that using an additive manufacturing process such as fused filament fabrication to make 3-D objects from blends of polypropylene and one or more semi-amorphous polymers can produce an object that has reduced shrinkage, reduced warpage, and that is capable of forming a uniform diameter printing filament. [0030] Typically, the polypropylene(s) is present in the compositions of the present invention at from 40 wt% to 99.9 wt% (based upon the weight of the polypropylene(s) and the semi- amorphous polymer(s)) in one embodiment, and from 50 wt% to 99 wt% in another embodiment, and from 60 wt% to 98 wt% in yet another embodiment, and from 70 wt% to 97 wt% in yet another embodiment, and from 80 wt% to 97 wt% in yet another embodiment, and from 90 wt% to 98 wt% in yet another embodiment, wherein a desirable range may be any combination of any upper wt% limit with any lower wt% limit described herein.

[0031] In another embodiment, the semi-amorphous polymer is present at 60 to 0.01 weight % (based upon the weight of the polypropylene and the semi-amorphous polymer), in one embodiment 50 wt% to 1 wt%, in another embodiment 40 wt% to 1 wt%, in yet another embodiment 30 wt% to 2 wt %, alternately 20 wt% to 3 wt %, in yet another embodiment 15 wt% to 1 wt%, in yet another embodiment 10 wt% to 4 wt%; in yet another embodiment, wherein a desirable range may be any combination of any upper wt% limit with any lower wt% limit described herein.

Semi-Amorphous Polymer

[0032] In some examples, blends of this invention comprise from 1 wt% to 50 wt% of one or more semi-amorphous polymers (based upon the weight of the semi-crystalline and semi- amorphous polymers), preferably from greater than 10 wt% to 40 wt%, preferably from 15 wt% to 40 wt%, preferably from 25 wt% to 40 wt%. In some embodiments, the semi-amorphous polymers comprise propylene and from 5 wt% to 25 wt% of one or more C2 to C10 alpha-olefin comonomers, preferably from 10 wt% to 25 wt% of one or more C2 to C10 alpha-olefin comonomers preferably from 10 wt% to 20 wt%, preferably from 12 wt% to 20 wt%, based upon the weight of the semi-amorphous polymers. Preferably the alpha olefin comonomer is a C2 to C10 alpha olefin selected from the group consisting of ethylene, butene, pentene, hexene, heptene, octene, nonene, and decene, preferably ethylene, butene, hexene, and octene, preferably ethylene. [0033] The ethylene content of the semi-amorphous polymers can be measured as follows. A thin homogeneous film is pressed at a temperature of about 150°C or greater, then mounted on a Perkin Elmer PE 1760 infrared spectrophotometer. A full spectrum of the sample from 600 cm^'1 to 4000 cm^'1 is recorded and the monomer weight percent of ethylene can be calculated according to the following equation: Ethylene wt% = 82.585 -111.987X + 30.045 X², wherein X is the ratio of the peak height at 1155 cm^'1 and peak height at either 722 cm^'1 or 732 cm^'1, whichever is higher. [0034] The semi-amorphous polymers can have a percent crystallinity of 2.5 to 25%, preferably from 5 to 23%, preferably from 5 to 20%. Percent crystallinity is determined according to the DSC procedure described above.

[0035] The semi-amorphous polymers can have a melt flow rate of 0.1 to 200 dg/min, preferably 0.1 to 100 dg/min, preferably 0.5 to 50, preferably 1 to 25, preferably 1 to 20 dg/min (as measured by ASTM D1238-13, 2.16 kg and 230°C).

[0036] The semi-amorphous polymers can have a DSC melting point (Tm) of 105°C or less, preferably 90°C or less, preferably between 25 and 90°C, preferably between 30 and 80°C, preferably between 35 and 75°C, as measured by the DSC procedure described above.

[0037] The semi-amorphous polymers can have an intermolecular composition distribution of 75% or more, preferably 80% or more, preferably 85% or more, preferably 90% or more by weight of the polymer isolated as one or two adjacent, soluble fractions with the balance of the polymer in immediately preceding or succeeding fractions; and wherein each of these fractions has a weight % comonomer content with a difference of no greater than 20 wt% (relative), preferably 10% (relative), of the average weight % comonomer of the copolymer. The fractions are obtained at temperature increases of approximately 8°C between stages. The intermolecular composition distribution of the copolymer is determined by thermal fractionation in hexane as follows: about 30 grams of the semi-amorphous polymer is cut into small cubes of about 1/8 inch (0.32 cm) on the side and is then introduced into a thick walled glass bottle closed with screw cap along with 50 mg of Irganoxl076, an antioxidant commercially available from Ciba-Geigy Corporation. Then, 425 ml of hexane (a principal mixture of normal and iso isomers) is added to the contents of the bottle and the sealed bottle is maintained at about 23°C for 24 hours. At the end of this period, the solution is decanted, and the residue is treated with additional hexane for an additional 24 hours at 23°C. At the end of this period, the two hexane solutions are combined and evaporated to yield a residue of the polymer soluble at 23°C. To the residue is added sufficient hexane to bring the volume to 425 ml and the bottle is maintained at about 31°C for 24 hours in a covered circulating water bath. The soluble polymer is decanted, and the additional amount of hexane is added for another 24 hours at about 31°C prior to decanting. In this manner, fractions of the semi- amorphous polymer soluble at 40°C, 48°C, 55°C, and 62°C are obtained at temperature increases of approximately 8°C between stages. The soluble polymers are dried, weighed and analyzed for composition, as wt% ethylene content. To produce a copolymer having the desired narrow composition, it is beneficial if (1) a single sited metallocene catalyst is used which allows only a single statistical mode of addition of the first and second monomer sequences and (2) the copolymer is well-mixed in a continuous flow stirred tank polymerization reactor which allows only a single polymerization environment for substantially all of the polymer chains of the copolymer.

[0038] The semi-amorphous polymers can have a molecular weight distribution (Mw/Mn) of Mw/Mn of less than 5, preferably between 1.5 and 4, preferably between 1.5 and 3.

[0039] In another embodiment polymers that are useful in this invention as semi-amorphous polymers include homopolymers and random copolymers of propylene having a heat of fusion as determined by Differential Scanning Calorimetry (DSC) of less than 70 J/g, an MFR of 50 dg/min or less, and contain stereoregular propylene crystallinity preferably isotactic stereoregular propylene crystallinity. In another embodiment the semi-amorphous polymers is a random copolymer of propylene and at least one comonomer selected from ethylene, C4-C12 a-olefms, and combinations thereof. Preferably the random copolymers of propylene comprises from 10 wt% to

25 wt% polymerized ethylene units, based on the total weight of the polymer; has a narrow intermolecular composition distribution (e.g. 75% or more by thermal fractionation); has a melting point (Tm) of from 25°C to 120°C, or from 35°C to 80°C; has a heat of fusion within the range having an upper limit of 70 J/g or 25 J/g and a lower limit of 1 J/g or 3 J/g; has a molecular weight distribution Mw/Mn of from 1.8 to 4.5; and has a melt flow rate of less than 40 dg/min, or less than 20 dg/min (as measured at 230°C, and 2.16 kg, ASTM 1238).

[0040] A particularly preferred polymer useful in the present invention as a semi-amorphous polymer is a polymer with a moderate level of crystallinity due to stereoregular propylene sequences. The polymer can be: (A) a propylene homopolymer in which the crystallinity is disrupted in some manner such as by regio-inversions and stereo defects; (B) a random propylene copolymer in which the propylene crystallinity is disrupted at least in part by comonomers; or (C) a combination of (A) and (B).

[0041] In one embodiment, the useful semi-amorphous polymers described above further include a non-conjugated diene monomer to aid in later chemical modification of the blend composition (such as crosslinking). The amount of diene present in the polymer is preferably less than 10% by weight, and more preferably less than 5% by weight. The diene may be any non- conjugated diene which is commonly used in ethylene propylene copolymers including, but not limited to, ethylidene norbornene, vinyl norbomene, and dicyclopentadiene.

[0042] In one embodiment, the semi-amorphous polymer is a random propylene copolymer having a narrow composition distribution. In another embodiment, the semi-amorphous polymer is a random propylene copolymer having a narrow composition distribution and a melting point of from 25°C to 120°C, preferably 25°C to 90°C. The copolymer is described as random because for a polymer comprising propylene, comonomer, and optionally diene, the number and distribution of comonomer residues is consistent with the random statistical polymerization of the monomers. In stereoblock structures, the number of block monomer residues of any one kind adjacent to one another is greater than predicted from a statistical distribution in random copolymers with a similar composition. Historical ethylene-propylene copolymers with stereoblock structure have a distribution of ethylene residues consistent with these blocky structures rather than a random statistical distribution of the monomer residues in the polymer. The intermolecular composition distribution (i.e., randomness) of the copolymer may be determined by ¹³C NMR, which locates the comonomer residues in relation to the neighboring propylene residues. The intermolecular composition distribution of the copolymer is determined by thermal fractionation in hexane as previously described.

[0043] In another embodiment, the semi-amorphous polymers useful herein can have a heat of fusion as determined by DSC described above of 80 J/g or less, 75 J/g or less, 70 J/g or less, or from 1 to 65 J/g, or from 2 to 50 J/g, or from 4 to 45 J/g.

[0044] In another embodiment, the semi-amorphous polymers useful herein have a weight average molecular weight of from 20,000 to 1,000,000 g/mol, preferably from 50,000 to 500,000 g/mol, preferably from 125,000 to 400,000g/mol. [0045] Preferred semi-amorphous polymers used in embodiments of the present invention have a propylene tacticity index (m/r) ranging from a lower limit of 4 or 6 to an upper limit of about 8, 10, or 12. The propylene tacticity index, expressed herein as "m/r", is determined by ¹³C nuclear magnetic resonance (NMR). The propylene tacticity index m/r is calculated as defined in

H.N. Cheng, Macromolecules , 17, 1950 (1984). The designation “m” or “r” describes the stereochemistry of pairs of contiguous propylene groups, “m” referring to meso and “r” to racemic. An m/r ratio of 0 to less than 1.0 generally describes a syndiotactic polymer, and an m/r ratio of

I.0 an atactic material, and an m/r ratio of greater than 1.0 an isotactic material. An isotactic material theoretically may have a ratio approaching infinity, and many by-product atactic polymers have sufficient isotactic content to result in ratios of greater than 50.

[0046] In a preferred embodiment, the preferred semi-amorphous polymers can have isotactic stereoregular propylene crystallinity. The term "stereoregular" as used herein means that the predominant number, i.e. greater than 80%, of the units derived from propylene residues in the polypropylene exclusive of any other monomer such as ethylene, has the same 1,2 insertion and the stereochemical orientation of the pendant methyl groups is the same, either meso or racemic. [0047] Preferred semi-amorphous polymers useful in this invention have an mm triad tacticity index of three propylene units, as measured by ¹³C NMR, of 75% or greater, 80% or greater, 82% or greater, 85% or greater, or 90% or greater. The mm triad tacticity index of a polymer is the relative tacticity of a sequence of three adjacent propylene units, a chain consisting of head to tail bonds, expressed as a binary combination of m and r sequences. It is expressed for semi- amorphous copolymers of the present invention as the ratio of the number of units of the specified tacticity to all of the propylene triads in the copolymer. The mm triad tacticity index (mm fraction) of a propylene copolymer can be determined from a ¹³C NMR spectrum of the propylene copolymer and the following formula:

PPP(mm) mm Fraction = -

PPP(mm) + PPP(mr) + PPP(rr) where PPP(mm), PPP(mr) and PPP(rr) denote peak areas derived from the methyl groups of the second units in the following three propylene unit chains consisting of head-to-tail bonds:

[0048] The ¹³C NMR spectrum of the propylene copolymer is measured as described in US Patent No. 5,504,172. The spectrum relating to the methyl carbon region (19-23 parts per million (ppm)) can be divided into a first region (21.2-21.9 ppm), a second region (20.3-21.0 ppm) and a third region (19.5-20.3 ppm). Each peak in the spectrum was assigned with reference to an article in the journal Polymer, v.30 (1989), page 1350. In the first region, the methyl group of the second unit in the three propylene unit chain represented by PPP (mm) resonates. In the second region, the methyl group of the second unit in the three propylene unit chain represented by PPP (mr) resonates, and the methyl group (PPE-methyl group) of a propylene unit whose adjacent units are a propylene unit and an ethylene unit resonates (in the vicinity of 20.7 ppm). In the third region, the methyl group of the second unit in the three propylene unit chain represented by PPP (rr) resonates, and the methyl group (EPE-methyl group) of a propylene unit whose adjacent units are ethylene units resonates (in the vicinity of 19.8 ppm). The calculation of the mm triad tacticity is outlined in the techniques shown in US Patent No. 5,504,172. Subtraction of the peak areas for the error in propylene insertions (both 2,1 and 1,3) from peak areas from the total peak areas of the second region and the third region, the peak areas based on the 3 propylene units-chains (PPP(mr) and PPP(rr)) consisting of head-to-tail bonds can be obtained. Thus, the peak areas of PPP(mm), PPP(mr) and PPP(rr) can be evaluated, and hence the mm triad tacticity of the propylene unit chain consisting of head-to-tail bonds can be determined.

[0049] In another embodiment polymers that are useful in this invention as semi-amorphous polymers include homopolymers and random copolymers of propylene having a heat of fusion as determined by Differential Scanning Calorimetry (DSC) of less than 70 J/g, an MFR of 50 dg/min or less, and contain stereoregular propylene crystallinity preferably isotactic stereoregular propylene crystallinity. In another embodiment the semi-amorphous polymer is a random copolymer of propylene and at least one comonomer selected from ethylene, C4-C12 a-olefins, and combinations thereof. Preferably the random copolymers of propylene comprises from 10 wt% to 25 wt% polymerized ethylene units, based on the total weight of the semi-amorphous polymer; has a narrow intermolecular composition distribution (e.g. 75 % or more); has a melting point (Tm) of from 25°C to 120°C, or from 35°C to 80°C; has a heat of fusion within the range having an upper limit of 70 J/g or 25 J/g and a lower limit of 1 J/g or 3 J/g; has a molecular weight distribution Mw/Mn of from 1.8 to 4.5; and has a melt flow rate of less than 40 dg/min, or less than 20 dg/min (as measured at 230°C, and 2.16 kg, ASTM D-1238).

[0050] Preferred polymers useful as semi-amorphous copolymers in this invention are also those polymers described in detail as the "Second Polymer Component (SPC)" in WO 2000/069963, WO 2000/001766, WO 1999/007788, WO 2002/083753, and described in further detail as the "Propylene Olefin Copolymer" in WO 2000/001745, all of which are fully incorporated by reference herein.

[0051] Preferred semi-amorphous copolymers may be produced in a solution process using a metallocene catalyst as follows. In a preferred embodiment, a continuous solution polymerization process is used to produce copolymers of propylene and from 10 to 25 weight % ethylene preferably utilizing a metallocene catalyst, namely, 1, r-bis(4-triethylsilylphenyl)methylene- (cyclopentadienyl)(2,7-di-tertiary-butyl-9-fluorenyl)hafnium dimethyl with dimethylaniliniumtetrakis-(pentafluorophenyl) borate as an activator. An organoaluminum compound, namely, tri-n-octylaluminum, may be added as a scavenger to the monomer feedstreams prior to introduction into the polymerization process. For preferred polymers, dimethylsilylbis(indenyl)hafnium dimethyl is used in combination with dimethylaniliniumtetrakis(pentafluorophenyl) borate. In other embodiments, dimethylsilyl bis(2- methyl-5-phenylindenyl) zirconium di alkyl ( such as methyl) and or dimethylsilyl bis(2- methylindenyl)zirconium di alkyl (such as methyl) is used with an activator (dimethylaniliniumtetrakis(pentafluorophenyl) borate and or triaryl carbenium(pentafluorophenyl) borate). Preferably the solution polymerization is conducted in a single, or optionally in two, continuous stirred tank reactors connected in series with hexane used as the solvent. In addition, toluene may be added to increase the solubility of the co-catalyst. The feed is transferred to the first reactor at a reaction temperature between about 50°C to about 220°C. Hydrogen gas may also be added to the reactors as a further molecular weight regulator. If desired, polymer product is then transferred to a second reactor, which is operated at a temperature between about 50°C to 200°C. Additional monomers, solvent, metallocene catalyst, and activators can be fed to the second reactor.

[0052] Preferred semi-amorphous polymers may also be produced by the continuous solution polymerization process described in WO 2002/034795, advantageously in a single reactor and separated by liquid phase separation from the alkane solvent. Preferred semi-amorphous polymers may also be produced by the polymerization process described at page 6 lines 24-57 of EP 1003814B1.

[0053] Further detailed instructions on how to make such preferred semi-amorphous polymers can be found in WO 2002/083754.

[0054] Preferred semi-amorphous polymers useful herein are made using a metallocene catalyst system.

[0055] Preferred semi-amorphous polymers include VM™1000, VM™2000, and VM™3000 available from ExxonMobil Chemical Company in Houston, Texas.

Propylene Polymer

[0056] The semi-amorphous polymers described herein are blended with at least one propylene polymer to prepare the material used for additive manufacturing.

[0057] In one aspect of the invention, the polypropylene is selected from polypropylene homopolymer, polypropylene copolymers, and blends thereof. The homopolymer may be atactic polypropylene, isotactic polypropylene, syndiotactic polypropylene and blends thereof. The copolymer can be a random copolymer, a statistical copolymer, a block copolymer, and blends thereof. In particular, the inventive polymer blends described herein include impact copolymers, which may be physical blends or in situ blends with the polypropylene. The method of making the polypropylene is not critical, as it can be made by slurry, solution, gas phase or other suitable processes, and by using catalyst systems appropriate for the polymerization of polyolefins, such as Ziegler-Natta-type catalysts, metallocene-type catalysts, other appropriate catalyst systems or combinations thereof. In a preferred embodiment the propylene polymers are made by the catalysts, activators and processes described in US Pat. Nos. 6,342,566, 6,384,142, WO 2003/040201, WO 1997/019991 and US Pat. No. 5,741,563. Likewise the impact copolymers may be prepared by the process described in US Pat. Nos. 6,342,566, 6,384,142. Such catalysts are well known in the art, and are described in, for example, ZIEGLER CATALYSTS (Gerhard Fink, Rolf Miilhaupt and Hans H. Brintzinger, eds., Springer- Verlag 1995); Resconi et al, Selectivity in Propene Polymerization with Metallocene Catalysts, 100 CHEM. REV. 1253-1345 (2000); and I, II METALLOCENE-BASED POLYOLEFINS (Wiley & Sons 2000).

[0058] Preferred propylene homopolymers and propylene copolymers useful in this invention typically have:

1. an Mw of 30,000 to 2,000,000 g/mol preferably 50,000 to 1,000,000, more preferably 90,000 to 500,000, as measured by GPC as described below in the test methods; and/or

2. an Mw/Mn of 1 to 40, preferably 1.6 to 20, more preferably 1.8 to 10, more preferably 1.8 to 3 as measured by GPC as described below in the test methods; and/or

3. a Tm (second melt) of 30 to 200°C., preferably 30 to 185°C, preferably 50 to 175, more preferably 60 to 170 as measured by the DSC method described below in the test methods; and/or

4. a crystallinity of 5 to 80%, preferably 10 to 70, more preferably 20 to 60% as measured by the DSC method described below m the test methods; and/or

5. a glass transition temperature (Tg) of -40°C to 20°C, preferably ~2Q°C to 10°C, more preferably -10°C to 5^CC as measured by the DMTA method described below in the test methods; and/or

6. a heat of fusion (Hi) of 180 J/g or less, preferably 20 to 150 J/g, more preferably 40 to 120 J/g as measured by the DSC method described below in the test methods; and/or

7. a crystallization temperature (Tc) of 15 to 120°C, preferably 20 to 115°C, more preferably 25 to 110°C, preferably 60 to 145°C, as measured by the method described below in the test methods; and/or

8. a heat deflection temperature of 45 to 140°C, preferably 60 to 135°C, more preferably 75 to 125°C as measured by the method described below in the test methods, and/or

9. a Rockwell hardness (R scale) of 25 or more, preferably 40 or more, preferably 60 or more, preferably 80 or more, preferably 100 or more, preferably from 25 to 125; and/or

10. a percent crystallinity of at least 30%, preferably at least 40%, alternatively at least 50%, as measured by the method described below m the test methods; and/or ] ] . a percent amorphous content of at least 50%, alternatively at least 60%, alternatively at least 70%, even alternatively between 50 and 95%, or 70% or less, preferably 60% or less, preferably 50% or less as determined by subtracting the percent crystallinity from 100, and/or

12. a branching index (g^') of 0.98 or less, alternately 0,96 or less, alternately 0.95 or less, alternately 0.93 or less, alternately 0.90 or less, alternately 0.85 or less, alternately 0.80 or less, alternately 0.75 or less, alternately 0.70 or less, alternately 0.65 or less, alternately 0,60 or less, alternately 0.55 or less.

[0059] In one embodiment the propylene homopolymer can have a molecular weight distribution (Mw/Mn) of up to 40, preferably ranging from 1.5 to 10, and from 1.8 to 7 in another embodiment, and from 1.9 to 5 in yet another embodiment, and from 2.0 to 4 in yet another embodiment. In another embodiment the propylene homopolymer has a Gardner impact strength, tested on 0.125 inch disk at 23°C, that may range from 20 in-lb to 1000 in-lb in one embodiment, and from 30 in-lb to 500 in-lb in another embodiment, and from 40 in-lb to 400 in-lb in yet another embodiment. In yet another embodiment, the 1% secant flexural modulus may range from 100 MPa to 2,300 MPa, and from 200 MPa to 2,100 MPa in another embodiment, and from 300 MPa to 2,000 MPa in yet another embodiment, wherein a desirable polypropylene may exhibit any combination of any upper flexural modulus limit with any lower flexural modulus limit. The melt flow rate (MFR) (ASTM D 1238, 230°C, 2.16 kg) of preferred propylene polymers range from 0.1 dg/min to 2500 dg/min in one embodiment, and from 0.3 to 500 dg/min in another embodiment. [0060] The polypropylene homopolymer or propylene copolymer useful in the present invention may have some level of isotacticity. Thus, in one embodiment, a polyolefin comprising isotactic polypropylene is a useful polymer in the invention of this patent, and similarly, highly isotactic polypropylene is useful in another embodiment. As used herein, “isotactic” is defined as having at least 10% isotactic pentads according to analysis by ¹³C-NMR as described in the test methods below. As used herein, “highly isotactic” is defined as having at least 60% isotactic pentads according to analysis by ¹³C-NMR. In a desirable embodiment, a polypropylene homopolymer having at least 85% isotacticity is the polyolefin, and at least 90% isotacticity in yet another embodiment.

[0061] In another desirable embodiment, a polypropylene homopolymer has at least 85% syndiotacticity, and at least 90% syndiotacticity in yet another embodiment. As used herein, “syndiotactic” is defined as having at least 10% syndiotactic pentads according to analysis by ¹³C-NMR as described in the test methods below. As used herein, “highly syndiotactic” is defined as having at least 60% syndiotactic pentads according to analysis by ¹³C-NMR.

[0062] In another embodiment the propylene homoploymer may be isotactic, highly isotactic, syndiotactic, highly syndiotactic or atactic. Atactic polypropylene is defined to be less than 10% isotactic or syndiotactic pentads. Preferred atactic polypropylenes typically have an Mw of 20,000 up to 1,000,000.

[0063] The polypropylene can be unimodal or multimodal with respect to one or more of molecular weight distribution, comonomer distribution or density distribution. A multimodal polyolefin may have at least two polymer components which have different weight average molecular weight, preferably a lower weight average molecular weight (LMW) and a higher weight average molecular weight (HMW). A unimodal polyolefin is typically prepared using a single stage polymerization, e.g. solution, slurry or gas phase polymerization, in a manner well- known in the art. A multimodal (e.g. bimodal) polypropylene can be produced by mechanically blending two or more, separately prepared polymer components or by in situ blending in a multistage polymerization process during the preparation process of the polymer components. Both mechanical and in situ blending are well-known in the field. A multistage polymerization process may preferably be carried out in a series of reactors, such as a loop reactor which may be a slurry reactor and/or one or more gas phase reactor(s). Preferably a loop reactor and at least one gas phase reactor is used. The polymerization can also be preceded by a pre-polymerization step. [0064] Preferred propylene polymers useful herein include those produced by metallocene catalyst systems including those propylene polymers having a composition distribution breadth index (CDBI) of 60% or more, preferably 70% or more, preferably 80% or more, preferably 90% or more. (CDBI) is measured as described in WO 1993/003093, with the modification that any fractions having a weight average molecular weight (Mw) below 25,000 g/mol are disregarded.) Preferred propylene polymers that can be used in the practice of this invention include those propylene polymers sold by ExxonMobil Chemical Company under the tradename ACHIEVE™. Particularly useful grades include ACHIEVE™ 3854, ACHIEVE™ 1654E1, ACHIEVE™3825, ACHIEVE™1605, available from ExxonMobil Chemical Company in Houston, Tex. Additional preferred HMPP's useful in the practice of this invention include those propylene homopolymers, and random copolymers available from ExxonMobil Chemical Company under the grade names: PP1024E4, PP1042, PP1032, PP1044, PP1052, PP1105E1, PP3155 and PP9852E1, PP9272, PP9513, PP9544, PP9562. In some instances, impact copolymers (ICP) can be utilized in the practice of this invention. Several are available from ExxonMobil Chemical Company (e.g. PP7032 E2). Preferred ICP's useful as the HMPP may also be those ICP's described in WO 2004/014998, particularly those described at page 37 to page 41.

[0065] In another embodiment of the invention, the propylene polymer is a copolymer, either random, or block, of propylene derived units and units selected from ethylene and C4 to C20 a-olefin derived units, typically from ethylene and C4 to C10 a-olefin derived units in another embodiment. The ethylene or C4 to C20 a-olefin derived units are present from 0.1 wt% to 50 wt% of the copolymer in one embodiment, and from 0.5 to 30 wt% in another embodiment, and from 1 to 15 wt% in yet another embodiment, and from 0.1 to 5 wt% in yet another embodiment, wherein a desirable copolymer comprises ethylene and C4 to C20 a-olefin derived units in any combination of any upper wt% limit with any lower wt% limit described herein. The propylene copolymer will have a weight average molecular weight of from greater than 8,000 g/mol in one embodiment, and greater than 10,000 g/mol in another embodiment, and greater than 12,000 g/mol in yet another embodiment, and greater than 20,000 g/mol in yet another embodiment, and less than 1,000,000 g/mol in yet another embodiment, and less than 800,000 in yet another embodiment, wherein a desirable copolymer may comprise any upper molecular weight limit with any lower molecular weight limit described herein.

[0066] Particularly desirable propylene copolymers have a molecular weight distribution (Mw/Mn) ranging from 1.5 to 10, and from 1.6 to 7 in another embodiment, and from 1.7 to 5 in yet another embodiment, and from 1.8 to 4 in yet another embodiment. The Gardner impact strength, tested on 0.125 inch disk at 23°C, of the propylene copolymer may range from 20 in-lb to 1000 in-lb in one embodiment, and from 30 in-lb to 500 in-lb in another embodiment, and from 40 in-lb to 400 in-lb in yet another embodiment. In yet another embodiment, the 1% secant flexural modulus of the propylene copolymer ranges from 100 MPa to 2,300 MPa, and from 200 MPa to 2,100 MPa in another embodiment, and from 300 MPa to 2,000 MPa in yet another embodiment, wherein a desirable polyolefin may exhibit any combination of any upper flexural modulus limit with any lower flexural modulus limit. The melt flow rate (MFR) (ASTMD 1238, 230°C, 2.16 kg) of propylene copolymer ranges from 0.1 dg/min to 2500 dg/min in one embodiment, and from 0.3 to 500 dg/min in another embodiment. [0067] In another embodiment the propylene polymer may be a propylene copolymer comprising propylene and one or more other monomers selected from the group consisting of ethylene and C₄ to C₂₀ linear, branched or cyclic monomers, and in some embodiments is a C₄ to C₁₂ linear or branched alpha-olefin, preferably butene, pentene, hexene, heptene, octene, nonene, decene, dodecene, 4-methyl-pentene- 1,3 -methyl pentene-l,3,5,5-trimethyl-hexene-l, and the like. The monomers may be present at up to 50 weight %, preferably from 0 to 40 weight %, more preferably from 0.5 to 30 weight %, more preferably from 2 to 30 weight %, more preferably from 5 to 20 weight %.

[0068] Preferred linear alpha-olefins useful as comonomers for the propylene copolymers useful in this invention include C₃ to C₈ alpha-olefins, more preferably 1 -butene, 1 -hexene, and 1 -octene, even more preferably 1 -butene. Preferred linear alpha-olefins useful as comonomers for the butene copolymers useful in this invention include C₃ to C₈ alpha-olefins, more preferably propylene, 1 -hexene, and 1 -octene, even more preferably propylene. Preferred branched alpha- olefins include 4-methyl- 1 -pentene, 3 -methyl- 1 -pentene, and 3, 5, 5 -trimethyl- 1 -hexene, 5-ethyl-l- nonene. Preferred aromatic-group-containing monomers contain up to 30 carbon atoms. Suitable aromatic-group-containing monomers comprise at least one aromatic structure, preferably from one to three, more preferably a phenyl, indenyl, fluorenyl, or naphthyl moiety. The aromatic- group-containing monomer further comprises at least one polymerizable double bond such that after polymerization, the aromatic structure will be pendant from the polymer backbone. The aromatic-group containing monomer may further be substituted with one or more hydrocarbyl groups including but not limited to C₁ to C₁₀ alkyl groups. Additionally, two adjacent substitutions may be joined to form a ring structure. Preferred aromatic-group-containing monomers contain at least one aromatic structure appended to a polymerizable olefinic moiety. Particularly preferred aromatic monomers include styrene, alpha-methylstyrene, para-alkylstyrenes, vinyltoluenes, vinylnaphthalene, allyl benzene, and indene, especially styrene, param ethyl styrene, 4-phenyl- 1- butene and allyl benzene.

[0069] Nonaromatic cyclic group containing monomers are also preferred. These monomers can contain up to 30 carbon atoms. Suitable non-aromatic cyclic group containing monomers preferably have at least one polymerizable olefinic group that is either pendant on the cyclic structure or is part of the cyclic structure. The cyclic structure may also be further substituted by one or more hydrocarbyl groups such as, but not limited to, C₁ to C₁₀ alkyl groups. Preferred non- aromatic cyclic group containing monomers include vinylcyclohexane, vinylcyclohexene, vinylnorbornene, ethylidene norbornene, cyclopentadiene, cyclopentene, cyclohexene, cyclobutene, vinyladamantane and the like.

[0070] Preferred diolefin comonomers useful in this invention include any hydrocarbon structure, preferably C4 to C30, having at least two unsaturated bonds, wherein at least two of the unsaturated bonds are readily incorporated into a polymer by either a stereospecific or a non stereospecific catalyst(s). It is further preferred that the diolefin monomers be selected from alpha, omega-diene monomers (i.e. di-vinyl monomers). More preferably, the diolefin monomers are linear di-vinyl monomers, most preferably those containing from 4 to 30 carbon atoms. Examples of preferred dienes include butadiene, pentadiene, hexadiene, heptadiene, octadiene, nonadiene, decadiene, undecadiene, dodecadiene, tridecadiene, tetradecadiene, pentadecadiene, hexadecadiene, heptadecadiene, octadecadiene, nonadecadiene, icosadiene, heneicosadiene, docosadiene, tricosadiene, tetracosadiene, pentacosadiene, hexacosadiene, heptacosadiene, octacosadiene, nonacosadiene, triacontadiene, particularly preferred dienes include 1,6-heptadiene, 1,7-octadiene, 1,8-nonadiene, 1,9-decadiene, 1,10-undecadiene, 1,11 -dodecadiene, 1,12-tridecadiene, 1,13 -tetradecadiene, and low molecular weight polybutadienes (Mw less than 1000 g/mol). Preferred cyclic dienes include cyclopentadiene, vinylnorbornene, norbornadiene, ethylidene norbornene, divinylbenzene, dicyclopentadiene or higher ring containing diolefins with or without substituents at various ring positions.

[0071] In a preferred embodiment one or more dienes are present in the polymer produced herein at up to 10 weight %, preferably at 0.00001 to 1.0 weight %, preferably 0.002 to 0.5 weight %, even more preferably 0.003 to 0.2 weight %, based upon the total weight of the composition. In some embodiments 500 ppm or less of diene is added to the polymerization, preferably 400 ppm or less, preferably or 300 ppm or less. In other embodiments at least 50 ppm of diene is added to the polymerization, or 100 ppm or more, or 150 ppm or more.

[0072] In another embodiment the propylene copolymer is a random copolymer, also known as an “RCP,” comprising propylene and up to 20 mole % of ethylene or a C4 to C20 olefin, preferably up to 20 mole % ethylene.

[0073] In another embodiment, the propylene copolymer is a propylene impact copolymers (“ICPs”) which can include a Component A and a Component B. Component A can be an isotactic propylene homopolymer, though small amounts of a comonomer may be used to obtain particular properties. Typically, such copolymers contain 10% by weight or less, preferably less than 6% by weight or less, comonomer such as ethylene, butene, hexene or octene. In some examples, less than 4% by weight ethylene is used. The end result is usually a product with lower stiffness but with some gain in impact strength compared to homopolymer Component A.

[0074] Component A can have a narrow molecular weight distribution Mw/Mn (“MWDI”), i.e., lower than 4.5, lower than 4.0, lower than 3.5, or 3.0 or lower. These molecular weight distributions can be obtained in the absence of visbreaking using peroxide or other post reactor treatment designed to reduce molecular weight. Component A can have a weight average molecular weight (Mw as determined by GPC) of at least 100,000, at least 200,000 and a melting point (Mp) of at least 145°C, at least 150°C, or at least 155°C.

[0075] Component B can have a copolymer comprising propylene and comonomer, preferably ethylene, although other propylene copolymers or terpolymers may be suitable depending on the particular product properties desired. For example, propylene/butene, hexene or octene copolymers may be used. In some examples, Component B is a copolymer comprising at least 20% by weight isotactic propylene, from about 20% by weight to about 70% by weight propylene, or from about 30% by weight to about 60% by weight propylene; and from about 30% to about 80% by weight comonomer or from about 40% to about 70% by weight comonomer, preferably ethylene. In some examples, Component B consists essentially of propylene and from about 20% to about 80% by weight ethylene, from about 30% to about 70% by weight ethylene, or from about 40% to about 60% by weight ethylene.

[0076] Component B can have an intrinsic viscosity greater than 1.00 dl/g, greater than 1.50 dl/g or greater than 2.00 d/g. The term “intrinsic viscosity” or “IV” is used conventionally herein to mean the viscosity of a solution of polymer such as Component B in a given solvent at a given temperature, when the polymer composition is at infinite dilution. According to the ASTM standard test method D 1601-78, IV measurement involves a standard capillary viscosity measuring device, in which the viscosity of a series of concentrations of the polymer in the solvent at the given temperature are determined. For Component B, decalin is a suitable solvent and a typical temperature is 135°C. From the values of the viscosity of solutions of varying concentrations, the “value” at infinite dilution can be determined by extrapolation.

[0077] Component B can have a composition distribution breadth index (CDBI) of greater than 60%, greater than 65%, greater than 70%, greater than 75%, or greater than 80%. CDBI is described in detail US Pat. No. 5,382,630 which is hereby fully incorporated by reference. CDBI is defined as the weight percent of the copolymer molecules having a comonomer content within 50% of the median total molar comonomer content.

[0078] The ICPs can be “reactor produced” meaning Components A and B are not physically or mechanically blended together after polymerization. Rather, they can be interpolymerized in at least one reactor. The final ICP as obtained from the reactor or reactors, however, can be blended with various other components including other polymers or additives.

[0079] The melt flow rate (“MFR”) of the ICPs depends on the desired end use but exemplary ranges can be from about 10.0 dg/min to about 4000.0 dg/min, from about 50.0 dg/min to about 3000.0 dg/min, from about 100.0 to about 2000.0, or from about 400.0 dg/min to about 2000.0 dg/min. MFR can be determined by a conventional procedure such as ASTM-1238 Cond. L. [0080] The ICPs can comprise from about 40% to about 95% by weight Component A and from about 5% to about 60% by weight Component B, from about 50% to about 90% by weight Component A and from about 10% to about 50% Component B, from about 60% to about 90% by weight Component A and from about 10% to about 40% by weight Component B. In some examples, the ICP consists essentially of Components A and B. The overall comonomer (preferably ethylene) content is preferably in the range of from about 30% to about 70% by weight or rom about 40% to about 60% by weight comonomer.

[0081] A variety of additives may be incorporated into the ICP for various purposes. Such additives include, for example, stabilizers, antioxidants, fillers, colorants, nucleating agents and mold release agents. Primary and secondary antioxidants include, for example, hindered phenols, hindered amines, and phosphates. Nucleating agents include, for example, sodium benzoate and talc. Dispersing agents such as Acrowax C can also be included. Slip agents include, for example, oleamide and erucamide. Catalyst deactivators are also commonly used, for example, calcium stearate, hydrotalcite, and calcium oxide.

[0082] The ICP compositions may be prepared by conventional polymerization techniques such as a two-step gas phase process using Ziegler-Natta catalysis. For example, see US Pat. No. 4,379,759 which is fully incorporated by reference. It is conceivable, although currently impractical, to produce ICPs in a single reactor. Preferably the ICPs of this invention are produced in reactors operated in series, and the second polymerization, polymerization of Component B, is preferably carried out in the gas phase. The first polymerization, polymerization of Component A, is preferably a liquid slurry or solution polymerization process.

[0083] Hydrogen may be added to one or both reactors to control molecular weight, IV and MFR. The use of hydrogen for such purposes is well known to those skilled in the art.

[0084] Metallocene catalyst systems may be used to produce the ICP compositions useful in this invention. Current particularly suitable metallocenes are those in the generic class of bridged, substituted bis(cyclopentadienyl) metallocenes, specifically bridged, substituted bis(indenyl) metallocenes known to produce high molecular weight, high melting, highly isotactic propylene polymers. Generally speaking, those of the generic class disclosed in US Pat. No. 5,770,753 (fully incorporated herein by reference) should be suitable.

Additives

[0085] Additives may be included in the polypropylene polymers, the semi-amorphous polymers, or the blends of the polypropylene polymers, the semi-amorphous polymers of this invention. Such additives and their use are generally well known in the art. These include those commonly employed with plastics such as heat stabilizers or antioxidants, plasticizers, neutralizers, slip agents, antiblock agents, pigments, antifogging agents, antistatic agents, clarifiers, nucleating agents, ultraviolet absorbers or light stabilizers, fillers and other additives in conventional amounts. Effective levels are known in the art and depend on the details of the base polymers, the fabrication mode and the end application. In some examples, fillers are present in the blend in an amount of up 50 wt%, up to 40 wt%, up to 30 wt%, up to 20 wt% based on a combined weight of the additives, the polypropylene polymers, and the semi-amorphous polymers. In some examples, fillers are present in the blend in an amount from about 1 wt% to about up 50 wt%, from about 5 wt% to about up 50 wt%, from about 10 wt% to about up 50 wt%, from about 20 wt% to about up 50 wt%, from about 1 wt% to about up 40 wt%, from about 5 wt% to about up 40 wt%, from about 10 wt% to about up 40 wt%, or from about 20 wt% to about up 40 wt% based on a combined weight of the additives, the polypropylene polymers, and the semi- amorphous polymers. In some examples, the filler can be calcium carbonate, magnesium carbonate, carbon black, silica, carbon-silica dual-phase filler, clay (layered silicates), lignin, carbon-nano-tubes, amorphous fillers, such as glass particle based fillers, starch based fillers, or combinations thereof. Foamins Agents

[0086] Foaming agents or additives may generally be divided into two classes: physical foaming agents and chemical foaming agents.

[0087] Physical foaming or blowing agents are generally gases such as carbon dioxide or nitrogen. Hydrocarbon gases, such as butane or pentane and fluorocarbon gases, such as trichlorofluromethane and dichlorodifluromethane are effective as physical blowing agents producing good quality foams. Because hydrocarbon and flurocarbon gases are viewed as presenting certain health and environmental concerns, the use of these gases is generally not the most desirable. More desirable physical blowing agents are carbon dioxide, nitrogen and argon. Physical blowing agents are utilized when low foam densities (£0.5 g/cm³) are required.

[0088] Chemical blowing agents allow the production of foamed produces having a density of generally greater than 0.5 g/cm³. Examples of chemical blowing agents include bicarbonate of soda (used typically in combination with citric acid), azodicarbonamide, sulfonyl hydrazide, sulfonyl semicarbazide. Bicarbonate of soda (endothermic agent) and azodicarbonamide (exothermic agent) are perhaps the most widely used chemical blowing agents.

[0089] When used at low levels, generally less than 1 wt%, and desirably around 0.25 wt% based on the weight of the polymer being foamed, chemical blowing agents may function as bubble nucleating agents and facilitate the formation of more uniformly sized bubble. This function is often utilized even when the primary foaming medium is a physical blowing agent, such as carbon dioxide gas. Talc can also be utilized for bubble nucleation.

Additive Manufacturing Processes and Devices

[0090] In an additive-manufacturing process, a model of the component that is being produced can be defined in any suitable manner. In some examples, the model can be designed with computer aided design software. The model can include 3-D numeric coordinates of the entire configuration of the component including both external and internal surfaces. The model can include a number of successive 2-D cross-sectional slices that together form the 3-D component. [0091] As such, additive manufacturing systems can be used to print or otherwise build three- dimensional ("3-D") parts from digital representations of the 3-D parts using one or more additive manufacturing techniques, such as fused filament fabrication. [0092] At an initial stage, the digital representation of the 3-D part is sliced into multiple horizontal layers. For each sliced layer, a path is then generated, which provides instructions for the additive manufacturing system to print the given layer.

[0093] Conventional fused filament fabrication printers designs and methods of operation can be found in US Pat. No. 7,604,470. In some examples, fused filament fabrication printers can be provided with one or more than one printing nozzle.

[0094] The 3-D printing filament used in the process can include a blend comprising polypropylene and a semi-amorphous polymer as described above. The polypropylene, the semi- amorphous polymer, and optional additives can be blended before being extruded into a filament or they can be blended as they are extruded into a filament. Any suitable processes to make 3-D filaments can be used, such as the process described in the examples below.

[0095] A three-dimensional structure can be formed through consecutive deposition of a filament using the extrusion nozzle. Examples of devices suitable for performing additive manufacturing processes include any commercially available device for such purpose. The three- dimensional structure can be built in layers, the depth of each layer typically being controllable by selectively adjusting the output from each extrusion nozzle.

[0096] The devices can utilize a computing system which implements design tools and/or topology optimization according to desired design aspects. The system can include a memory. The memory can store data. The memory can store executable instructions used to implement the topology optimization according to the desired design.

[0097] The specification can be transferred to an additive manufacturing device which performs the additive manufacturing techniques according to the specification in order to create the 3-D structure. While not required in all aspects, the additive manufacturing device can include processors that interpret the specification, and control other elements which apply the materials using robots, nozzles, lasers or the like to add the materials as layers or coatings to produce the 3-D structure.

[0098] The machine controller can control the operation of the extrusion nozzle along the "X," "Y," and "Z" axes via a plurality of drive motors. Each of these motors can be operating separately, or one or more of them may be operating simultaneously, depending upon the shape of the structure to be formed. Circular patterns for each layer can be generated by controlled movement along the "X" and "Y" axes of the build platform. [0099] The extrusion nozzle can be initially positioned a predetermined height above the build platform to form the first layer of the three-dimensional structure. The height of each subsequent layer can be then closely controlled. In some examples, thinner layers result in an overall smoother surface.

[0100] Thicker layers can increase the speed at which the structure is built. Layers as thin as 0.0001 mm can be formed. The layers can be formed horizontally, vertically, or in any other orientation. Depositing of the resin can take place along any of the three axes. The dispensing of the resin can take place along only the "X" - "Y" plane, until it is advantageous to deposit in the "X" "Z" plane or the "Z" " Y" plane. In some examples, the extrusion nozzle can be mounted along generally perpendicular to the build platform, and thus perpendicular to the "X" - "Y" plane of build platform. The first layer can take any shape dictated by the computer program. A second and each subsequent layer can take slightly different shapes, as dictated by the particular cross section for each layer from the computer program and layering software. In the pattern situation for each layer wherein each layer is formed only in a horizontal "X" - "Y" plane. A motor supporting the extrusion nozzle can be selectively actuated after each layer is formed to raise the nozzle incrementally along the "Z" axis in a closely controlled manner.

[0101] The multiple layers can be of uniform thickness, or the layers can vary in thickness, as necessary and appropriate for the forming of a particular structure. Also, the layers may each vary in thickness across the height of each layer.

[0102] Additive manufacturing systems build the solid part one layer at a time. Typical layer thicknesses range from about 0.001 to about 1,000,000 mm, from about 0.001 to about 1,000 mm, from about 0.001 to about 100 mm. Depending on the design, the layer can be thicker or thinner as practicable. The thickness can be adjusted depending on the process parameters, including the total number of layers that make up the structure, and the speed in which the structure is being built.

[0103] The device may operate generally according to a method comprising the following steps: inserting the filament into an additive manufacturing apparatus having a nozzle; heating the filament; and dispensing a fluid bead out of the filament out of the nozzle to manufacture a three- dimensional object.

[0104] In some examples, the 3-D component can contain from 2 to an unlimited number of engineered layers; from 2 to about 10,000 layers; from 2 to about 5,000 layers; from 2 to about 1,000 layers; from 2 to about 500 layers; from 2 to about 250 layers; from 2 to about 100 layers; from 10 to about 500 layers; from 50 to about 500 layers; from 100 to about 500 layers; or from 250 to about 500 layers. Each layer can have the same or different dimensions. Components having almost any shape can be prepared by additive manufacturing. In some examples, the 3-D printed component can be personal protective devices, medical facemasks, masks, mask components, tubing, goggles, shoes, hats or ventilator components.

[0105] This invention further relates to:

1. A process for making a three-dimensional object using an additive manufacturing process, comprising: preparing a blend comprising polypropylene and a semi-amorphous polymer, the semi- amorphous polymer comprising at least 60 wt% propylene-derived units and from about 5 to about 25 wt% ethylene-derived units, based on a total weight of the semi-amorphous polymer, and having a heat of fusion of less than about 80 J/g.; extruding the blend to make a filament; inserting the filament into an additive manufacturing apparatus having a nozzle; heating the filament; and dispensing a fluid bead of the filament out of the nozzle to manufacture the three- dimensional object.

2. The process of paragraph 1, wherein the polypropylene is an impact copolymer.

3. The process of paragraph 1 or paragraph 2, wherein the polypropylene has a g’_viS of less than 0.95.

4. The process of any of paragraphs 1 to 3, wherein the polypropylene is bimodal.

5. The process of any of paragraphs 1 to 4, wherein the polypropylene is an isotactic polypropylene.

6. The process of any of paragraphs 1 to 5, wherein the polypropylene is a random copolymer.

7. The process of any of paragraphs 1 to 6, wherein the polypropylene further comprises a foaming agent.

8. The process of any of paragraphs 1 to 7, wherein the blend comprises from about 50 wt% to about 99 wt% of the polypropylene and from 1 wt% to 50 wt% of the semi-amorphous polymer based on a total weight of the polypropylene and the semi-amorphous polymer.

9. A process for making a filament, comprising: preparing a blend comprising polypropylene and a semi-amorphous polymer, the semi- amorphous polymer comprising at least 60 wt% propylene-derived units and from about 5 to about 25 wt% ethylene-derived units, based on a total weight of the semi-amorphous polymer, and having a heat of fusion of less than about 80 J/g.; extruding the blend to make a filament, wherein the filament has a diameter from about 0.01 mm to about 1 m; and collecting the filament on a spool.

10. The process of paragraph 9, wherein the spool collects the filament at a rate from about 0.001 m/s to about 0.5m/s.

11. The process of paragraph 9 or paragraph 10, wherein the polypropylene is an impact copolymer.

12. The process of any of paragraphs 9 to 11, wherein the polypropylene has a g’_viS of less than 0.95.

13. The process of any of paragraphs 9 to 12, wherein the polypropylene is bimodal.

14. The process of any of paragraphs 9 to 13 wherein the polypropylene is an isotactic polypropylene.

15. The process of any of paragraphs 9 to 14, wherein the polypropylene is a random copolymer.

16. The process of any of paragraphs 9 to 15, wherein the polypropylene further comprises a foaming agent.

17. The process of any of paragraphs 9 to 16, wherein the blend comprises from about 50 wt% to about 99 wt% of the polypropylene and from 1 wt% to 50 wt% of the semi-amorphous polymer based on a total weight of the polypropylene and the semi-amorphous polymer.

18. A filament comprising, a blend of polypropylene and a semi-amorphous polymer, the semi-amorphous polymer comprising at least about 60 wt% propylene-derived units and from about 5 to about 25 wt% ethylene-derived units, based on a total weight of the semi-amorphous polymer, and having a heat of fusion of less than about 80 J/g, wherein the filament has a diameter from about 1 mm to about 3 mm.

19. The filament of paragraph 18, wherein the diameter of the filament varies by less than 0.1 mm per meter of the filament. 20. The filament of paragraph 18 or paragraph 19, wherein the polypropylene is an impact copolymer.

21. The filament of any of paragraphs 18 to 20, wherein the polypropylene has a g’_viS of less than 0.95.

22. The filament of any of paragraphs 18 to 21, wherein the polypropylene is bimodal.

23. The filament of any of paragraphs 18 to 22, wherein the polypropylene is an isotactic polypropylene.

24. The filament of any of paragraphs 18 to 23, wherein the polypropylene is a random copolymer.

25. The filament of any of paragraphs 18 to 24, wherein the polypropylene further comprises a foaming agent.

26. The filament of any of paragraphs 18 to 25, wherein the blend comprises from about 50 wt% to about 99 wt% of the polypropylene and from 1 wt% to 50 wt% of the semi-amorphous polymer based on a total weight of the polypropylene and the semi-amorphous polymer.

27. An article printed using the process of paragraph 1.

28. The article of paragraph 27 wherein the article is a mask or mask component.

Examples

[0106] Unless otherwise indicated, the distribution and the moments of molecular weight (Mw, Mn, Mz, Mw/Mn, etc.), the comonomer content and the branching index (gVi_s) are determined by using a high temperature Gel Permeation Chromatography (Polymer Char GPC-IR) equipped with a multiple-channel band-filter based Infrared detector IR5 with a multiple-channel band filter based infrared detector ensemble IR5 with band region covering from about 2700 cm^'1 to about 3000 cm^'1 (representing saturated C-H stretching vibration), an 18-angle light scattering detector and a viscometer. Three Agilent PLgel 10-pm Mixed-B LS columns are used to provide polymer separation. Reagent grade 1,2,4-trichlorobenzene (TCB) (from Sigma- Aldrich) comprising -300 ppm antioxidant butylated hydroxytoluene (BHT) can be used as the mobile phase at a nominal flow rate of -1.0 mL/min and a nominal injection volume of -200 pL. The whole system including transfer lines, columns, and detectors can be contained in an oven maintained at ~145°C. A given amount of sample can be weighed and sealed in a standard vial with -10 pL flow marker (heptane) added thereto. After loading the vial in the auto-sampler, the oligomer or polymer may automatically be dissolved in the instrument with -8 mL added TCB solvent at ~160°C with continuous shaking. The sample solution concentration can be from -0.2 to -2.0 mg/ml, with lower concentrations used for higher molecular weight samples. The concentration, c, at each point in the chromatogram can be calculated from the baseline subtracted IR5 broadband signal, /, using the equation: c=al, where a is the mass constant determined with polyethylene or polypropylene standards. The mass recovery can be calculated from the ratio of the integrated area of the concentration chromatography over elution volume and the injection mass which is equal to the pre-determined concentration multiplied by injection loop volume. The conventional molecular weight (IR MW) is determined by combining universal calibration relationship with the column calibration which is performed with a series of monodispersed polystyrene (PS) standards ranging from 700 to 10M gm/mole. The MW at each elution volume is calculated with following equation:

where the variables with subscript “PS” stand for polystyrene while those without a subscript are for the test samples. In this method, aps = 0.67 and Kps = 0.000175, a and K for other materials are as calculated and published in literature (Sun, T. et al. Macromolecules 2001, 34, 6812), except that for purposes of this invention and claims thereto, a = 0.695+(0.01*(wt. fraction propylene)) and K = 0.000579-(0.0003502*(wt. fraction propylene)) for ethylene-propylene copolymers and EADS copolymers, a = 0.695 and K = 0.000579 for linear ethylene polymers, a = 0.705 and K = 0.0002288 for linear propylene polymers. Concentrations are expressed in g/cm³, molecular weight is expressed in g/mole, and intrinsic viscosity (hence K in the Mark-Houwink equation) is expressed in dL/g unless otherwise noted.

[0107] The comonomer composition is determined by the ratio of the IR5 detector intensity corresponding to CTE and CH3 channel calibrated with a series of PE and PP homo/copolymer standards whose nominal value are predetermined by NMR or FTIR. In particular, this provides the methyls per 1000 total carbons (CH3/IOOOTC) as a function of molecular weight. The short- chain branch (SCB) content per lOOOTC (SCB/1000TC) is then computed as a function of molecular weight by applying a chain-end correction to the CH3/IOOOTC function, assuming each chain to be linear and terminated by a methyl group at each end. The weight % comonomer is then obtained from the following expression in which / is 0.3, 0.4, 0.6, 0.8, and so on for C3, C₄, C6, C8, and so on co-monomers, respectively:

[0108] The bulk composition of the polymer from the GPC-IR and GPC-4D analyses is obtained by considering the entire signals of the C¾ and CH2 channels between the integration limits of the concentration chromatogram. First, the following ratio is obtained

[0109] Then the same calibration of the CH3 and CH2 signal ratio, as mentioned previously in obtaining the CH3/IOOOTC as a function of molecular weight, is applied to obtain the bulk CH3/IOOOTC. A bulk methyl chain ends per lOOOTC (bulk Ctbend/IOOOTC) is obtained by weight-averaging the chain-end correction over the molecular-weight range. Then

bulk SCB/1000TC = bulk CH3/1000TC - bulk CH3end/1000TC and bulk SCB/1000TC is converted to bulk w2 in the same manner as described above.

[0110] The LS detector is the 18-angle Wyatt Technology High Temperature DAWN HELEOSII. The LS molecular weight (M) at each point in the chromatogram is determined by analyzing the LS output using the Zimm model for static light scattering {Light Scattering from Polymer Solutions,· Huglin, M. B., Ed.; Academic Press, 1972.):

Here, AR(0) is the measured excess Rayleigh scattering intensity at scattering angle Q, c is the polymer concentration determined from the IR5 analysis, A2 is the second virial coefficient, R(q) is the form factor for a monodisperse random coil, and K₀ is the optical constant for the system:

where NA is Avogadro’s number, and (dn/dc) is the refractive index increment for the system. The refractive index, n = 1.500 for TCB at 145°C and l = 665 nm. For analyzing polyethylene homopolymers, ethylene-hexene copolymers, and ethylene-octene copolymers, dn/dc = 0.1048 ml/mg and A2 = 0.0015; for analyzing ethylene-butene copolymers, dn/dc = 0.1048*(l-0.00126*w2) ml/mg and A2 = 0.0015 where w2 is weight percent butene comonomer. [0111] A high temperature Agilent (or Viscotek Corporation) viscometer, which has four capillaries arranged in a Wheatstone bridge configuration with two pressure transducers, is used to determine specific viscosity. One transducer measures the total pressure drop across the detector, and the other, positioned between the two sides of the bridge, measures a differential pressure. The specific viscosity, h₅, for the solution flowing through the viscometer is calculated from their outputs. The intrinsic viscosity, [h], at each point in the chromatogram is calculated from the equation [h]= %/c, where c is concentration and is determined from the IR5 broadband channel output. The viscosity MW at each point is calculated as , where a_ps

is 0.67 and K_ps is 0.000175.

[0112] The branching index (g'_vis) is calculated using the output of the GPC-IR5-LS-VIS method as follows. The average intrinsic viscosity, [r|]_avg, of the sample is calculated by:

where the summations are over the chromatographic slices, i, between the integration limits. The branching index g'_vis is defined as , where M_v is the viscosity-average molecular

weight based on molecular weights determined by LS analysis and the K and a are for the reference linear polymer, which are, for purposes of this invention and claims thereto, a = 0.695+(0.01*(wt. fraction propylene)) and K = 0.000579-(0.0003502*(wt. fraction propylene) for ethylene- propylene copolymers, and EADS copolymers, a = 0.695 and K = 0.000579 for linear ethylene polymers, a = 0.705 and K = 0.0002288 for linear propylene polymers. Concentrations are expressed in g/cm³, molecular weight is expressed in g/mole, and intrinsic viscosity (hence K in the Mark-Houwink equation) is expressed in dL/g unless otherwise noted. Calculation of the w2b values is as discussed above.

Differential Scanning Calorimetry (DSC )

[0113] The procedure for DSC determinations is as follows. 0.5 grams of polymer is weighed and pressed to a thickness of 15 to 20 mils (about 381-508 microns) at 140°C-150°C, using a “DSC mold” and MYLAR™ film as a backing sheet. The pressed polymer sample is allowed to cool to ambient temperatures by hanging in air (the MYLAR™ film backing sheet is not removed). The pressed polymer sample is then annealed at room temperature (about 23°C-25°C). A 15-20 mg disc is removed from the pressed polymer sample using a punch die and is placed in a 10 microliter aluminum sample pan. The disc sample is then placed in a DSC (Perkin Elmer Pyris 1 Thermal Analysis System) and is cooled to -100°C. The sample is heated at 10°C/min to attain a final temperature of 165°C. The thermal output, recorded as the area under the melting peak of the disc sample, is a measure of the heat of fusion and is expressed in Joules per gram (J/g) of polymer and is automatically calculated by the Perkin Elmer system. Linder these conditions, the melting profile shows two (2) maxims, the maxima at the highest temperature is taken as the melting point within the range of melting of the disc sample relative to a baseline measurement for the increasing heat capacity of the polymer as a function of temperature. The percent crystallinity (X%) is calculated using the formula: [area under the curve (in J/g) / H° (in J/g)] * 100, where H° is the heat of fusion for the homopolymer of the major monomer component. The values for H° are to be obtained from the Polymer Handbook, Fourth Edition, published by John Wiley and Sons, New York 1999, except that a value of 290 J/g is used as the equilibrium heat of fusion (H°) for 100% crystalline polyethylene, a value of 140 J/g is used as the equilibrium heat of fusion (H°) for 100% crystalline polybutene, and a value of 207 J/g (H°) is used as the heat of fusion for a 100% crystalline polypropylene.

[0114] Unless otherwise noted all melting points (T_m) are DSC second melt.

Example 1 Impact Copolymer/Semi-Amorphous Propylene Filament fabrication description

[0115] Filaments of all examples were prepared using ThermoFisher Process 11 Parallel Twin- Screw Extruder, and spooler. The extrusion and spooler conditions used are tabulated in Table 2. Extrusion is a process used to create objects of a fixed cross-sectional profile. In a typical extrusion process, a material is pushed through a die of the desired cross-section. For each filament, 200 gm weight of the example resins in pellet form were fed into the extruder hopper, and then extruded out from a circular die with 3 mm diameter. By controlling the take-off speed of the spooler, the diameter of the filament is adjusted to be 2.85 mm ± 0.1 mm measured by Neiko 01407A Electronic Digital Caliper.

FDM printed parts preparation and 3D printing process description

[0116] All Fused Deposition Modeling (FDM) specimens were fabricated with an Airwolf3D^® Axiom Single Head 3-D Printer. The geometry for the specimens investigated in this patent were ISO 37 Type 3 tensile bars. Dassault Systems SolidWorks software, which is a computer-aided design (CAD) package, was first used to create 3-D printable model with the dimension of ISO 37 Type 3 tensile bar. Then, the CAD model is tessellated and exported in STL format. The STL file was then sliced using Repetier Host software from Hot-World GmbH & Co. KG to convert the STL file into G-code, which is the standard language for 3-D printers. G-code is a numerically controlled programming language that contains commands to move parts within the printer. After filament is loaded to the 3-D printer, and 3-D printer is set up following printing conditions tabulated in Table 2, the FDM specimens were able to be produced. The properties of the FDM specimens are listed in Table 3.

Table 1: Resin properties.

Injection molding description

[0117] In order to measure the reference strength and behavior of the filament materials, for comparisons with FDM, additional specimens were fabricated by injection molding. Mold cavity dimensions were the same as those described for the FDM specimens, which is the ISO 37 Type 3 Tensile bar. All molded specimens were fabricated from the same FDM example resin pellets. The pellets were then fed into the hopper of a BOY XS injection molding machine. Molding parameters were set to the industrial recommended values for example resins, including nozzle temperature mold preheat temperature of 120°C, clamping force of 71 kN (16,000 lb), and injection pressure of 41 MPa (6,000 psi). Ten replicate specimens were molded for each of the five tests. Test methods

[0118] Tensile tests were performed on an Instron Autox750 Automatic Contacting Extensometer with 0.001 N force accuracy. The machine has a lOkN load force capacity. Instron Bluehill software was used to record the data.

Table 3: Tensile property and flexural properties for parts at indicated manufacturing process.

Example 2 Lons Chain Branching Polypropylene/ Semi-Amorphous Propylene Blends

Table 4: resin properties.

[0119] Filaments of all examples were prepared using ThermoFisher Process 11 Parallel Twin- Screw Extruder, and spooler. The extrusion and spooler conditions used are tabulated in Table 2. Extrusion is a process used to create objects of a fixed cross-sectional profile. In a typical extrusion process, a material is pushed through a die of the desired cross-section. For each filament, 200 gm weight of the example resins in pellet form were fed into the extruder hopper, and then extruded out from a circular die with 3 mm diameter. By controlling the take-off speed of the spooler, the diameter of the filament is adjusted to be 2.85 mm ± 0.1 mm measured by Neiko 01407A Electronic Digital Caliper.

[0120] E6 could not be make into filament due to the high melt flow rate. E7 was made into a filament with very low efficiency and a low temperature profile (100-150°C). Energy consumption and throughput are two main concerns for compounding processes. Lower energy consumption and higher throughput could help compounders create more value with reduced cost and increased productivity. In an extrusion process, the compounding processability could be quantified by torque. As shown in Table 5, the same filament fabrication conditions and temperature profiles were used in the extrusion process for comparing torques. The torques decreases with increasing concentration of Vistamaxx™ performance polymers, which suggests that the compounding process was improved.

[0121] All Fused Deposition Modeling (FDM) specimens were fabricated with an Airwolf3D^® Axiom Single Head 3-D Printer. The geometry for the specimens investigated in this patent were ISO 37 Type 3 tensile bars. Dassault Systems SolidWorks software, which is a computer-aided design (CAD) package, was first used to create 3-D printable model with the dimension of ISO 37 Type 3 tensile bar. Then, the CAD model is tessellated and exported in STL format. The STL file was then sliced using Repetier Host software from Hot-World GmbH & Co. KG to convert the STL file into G-code, which is the standard language for 3D printers. G-code is a numerically controlled programming language that contains commands to move parts within the printer. After filament is loaded to the 3-D printer, and 3-D printer is set up following printing conditions tabulated in Table 5, the FDM specimens were able to be produced. The properties of the FDM specimens are listed in Table 3.

Table 5

Table 6: Tensile property and flexural properties for parts at indicated manufacturing process.

[0122] E5, E6 and E7 FDM specimens could not be manufactured because they did not have enough melt strength to flow out of the FDM nozzle.

Claims

CLAIMS: What is claimed is:

1. A process, comprising: preparing a blend comprising polypropylene and a semi-amorphous polymer, the semi- amorphous polymer comprising at least 60 wt% propylene-derived units and from about 5 to about 25 wt% ethylene-derived units, based on a total weight of the semi-amorphous polymer, and having a heat of fusion of less than about 80 J/g; and extruding the blend to make a filament, wherein the filament has a diameter from about 0.01 mm to about lm.

2. The process of claim 1, further comprising: inserting the filament into an additive manufacturing apparatus having a nozzle; heating the filament; and dispensing a fluid bead of the filament out of the nozzle to manufacture a three-dimensional object.

3. The process of claim 1, further comprising collecting the filament on a spool, wherein the spool collects the filament at a rate from about 0.001 m/s to about 0.5 m/s.

4. The process of claim 1, wherein the polypropylene is an impact copolymer.

5. The process of claim 1, wherein the polypropylene has a g’_viS of less than 0.95.

6. The process of claim 1, wherein the polypropylene is bimodal.

7. The process of any of claim 1, wherein the polypropylene is an isotactic polypropylene.

8. The process of any of claim 1, wherein the polypropylene is a random copolymer.

9. The process of any of claim 1, wherein the polypropylene further comprises a foaming agent.

10. The process of any of claim 1, wherein the blend comprises from 1 wt% to 50 wt% of the semi-amorphous polymer based on a total weight of the polypropylene and the semi-amorphous polymer.

11. A filament comprising, a blend of polypropylene and a semi-amorphous polymer, the semi- amorphous polymer comprising at least about 60 wt% propylene-derived units and from about 5 to about 25 wt% ethylene-derived units, based on a total weight of the semi-amorphous polymer, and having a heat of fusion of less than about 80 J/g, wherein the filament has a diameter from about 1 mm to about 3 mm.

12. The filament of claim 11, wherein the diameter of the filament varies by less than 0.1 mm per meter of the filament.

13. The filament of claim 11, wherein the polypropylene is an impact copolymer.

14. The filament of claim 11, wherein the polypropylene has a g’_viS of less than 0.95.

15. The filament of claim 11, wherein the polypropylene is bimodal, isotactic polypropylene, or a random copolymer.

16. The filament of claim 11, wherein the blend comprises from 1 wt% to 50 wt% of the semi- amorphous polymer based on a total weight of the polypropylene and the semi-amorphous polymer.