WO2022010623A1 - Processes for making 3-d objects from blends of polyethylenes and cyclic-olefin copolymers - Google Patents

Abstract

This invention relates to a process for making a three-dimensional object using an additive manufacturing process. A blend is prepared that includes a polyethylene and a cyclic-olefin copolymer. The blend is extruded to make a filament. The filament can be inserted into an additive manufacturing apparatus with 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

TITLE: Processes for Making 3-D Objects from Blends of Polyethylenes and Cyclic- Olefin Copolymers

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. 63/048,985 filed July 7, 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 polyethylenes and cyclic-olefin copolymers.

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 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 thermoplastics (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: CN103980396 A, CN103980395B, JP2018035461A, JP2019203228 A, and WO2019/197582AE

SUMMARY OF INVENTION

[0009] A process for making objects using an additive manufacturing process is provided herein. In some examples, a blend can be prepared that can include polyethylene and a cyclic- olefin copolymer. 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, polyethylene and a cyclic-olefin copolymer 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 polyethylene and a cyclic-olefin copolymer. 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 one catalyst compound, 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” are used to indicate two or more catalyst compounds in the catalyst system. The term “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 (e.g., the definition of "substituted hydrocarbyl" etc.), the term “substituted” means that a hydrogen group has been replaced with at least one non-hydrogen group, such as a hydrocarbyl group, a heteroatom, or a heteroatom containing group. For example, substituted hydrocarbyl radicals can be radicals in which at least one hydrogen atom of the hydrocarbyl radical has been substituted with at least one functional group , such as halogen (such as Br, Cl, F or I) or at least one functional group such as -NR*2, -OR*, -SeR*, -TeR*, -PR*2, -AsR*2, -SbR*2, -SR*, -BR*2, -SiR*3, -GeR*3, -SnR*3, -PbR*3, -(CH2)q-SiR*3, and the like, where q is 1 to 10 and each R* is independently hydrogen, a hydrocarbyl or halocarbyl radical, and two or more R* may join together to form a substituted or unsubstituted completely saturated, partially unsaturated, or aromatic cyclic or polycyclic ring structure), or where at least one heteroatom has been inserted within a hydrocarbyl ring.

[0017] The term "substituted hydrocarbyl" means a hydrocarbyl radical in which at least one hydrogen atom of the hydrocarbyl radical has been substituted with at least one heteroatom (such as halogen, e.g., Br, Cl, F or I) or heteroatom-containing group (such as a functional group, e g., -NR*2, -OR*, -SeR*, -TeR*, -PR*2, -AsR*2, -SbR*2, -SR*, -BR*2, -SiR*3, -GeR*3, -SnR*3, -PbR*3, -(CH₂)q-SiR*3, and the like, where q is 1 to 10 and each R* is independently hydrogen, a hydrocarbyl or halocarbyl radical, and two or more R* may join together to form a substituted or unsubstituted completely saturated, partially unsaturated, or aromatic cyclic or polycyclic ring structure), or where at least one heteroatom has been inserted within a hydrocarbyl ring.

[0018] 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.

[0019] 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.

[0020] The term "aryl" or "aryl group" means a six carbon aromatic ring, 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. A substituted aryl group is an aryl group having 1 or more hydrogen groups replaced by a hydrocarbyl, substituted hydrocarbyl, heteroatom or heteroatom containing group.

[0021] 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.

[0022] 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. The term "substituted aromatic," means an aromatic group having 1 or more hydrogen groups replaced by a hydrocarbyl, substituted hydrocarbyl, heteroatom or heteroatom containing group.

[0023] 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.

[0024] 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), pg.27, (1985).

[0025] 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.

[0026] A “random copolymer” is a polymer having individual repeating units of one of the monomers present in a random or statistical distribution in the polymer chain. A “propylene random copolymer” is a propylene polymer having repeating units of the ethylene monomer(s) present in a random or statistical distribution in the polymer chain.

[0027] 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 M_w divided by M_n. Unless otherwise noted, all molecular weights (e.g., M_w, Mn, M_z) 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 ¹ 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.

[0028] As used herein, the term "polypropylene", "propylene polymer," or "PP" refers to homopolymers, copolymers, terpolymers, and interpolymers, typically comprising from 50 to 100 mol% propylene. Alternately the polypropylene comprises 50 to 100 weight % of propylene.

[0029] 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 in test methods below). Melting point (Tm), peak crystallization temperature (Tc), heat of fusion (Hf) and percent crystallinity are determined using differential scanning calorimetric (DSC) procedure in the test methods below.

[0030] This invention relates to a novel 3D printing material which can include a blend of a polyethylene and a cyclic-olefin copolymer.

[0031] It has been surprising and unexpectedly discovered that using an additive manufacturing process such as fused filament fabrication to make 3-D objects from a blend of a polyethylene and a cyclic-olefin copolymer can have reduced shrinkage, reduced warpage, and are capable of forming a uniform diameter printing filament. It has also been surprising and unexpectedly discovered that the properties of the cyclic-olefin copolymer can be varied to in tailor the mechanical properties of manufactured parts to meet physical property requirements for target applications.

[0032] Typically, the polyethylene is present in the blend at from 50 wt% to 99.9 wt% (based upon the weight of the polyethylene and the cyclic-olefin copolymer) in one embodiment, and from 50 wt% to 99 wt% in another embodiment, and from 50 wt% to 98 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 75 wt% to 99 wt%, and from and from 75 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.

[0033] In another embodiment, the cyclic-olefin copolymer is present in the blend at 50 to 0 1 wt% (the polyethylene and the cyclic-olefin copolymer), in one embodiment 50 to 1 wt%, in another embodiment 50 to 2 wt%, in another embodiment 40 to 1 wt%, in yet another embodiment 30 to 2 wt%, in yet another embodiment 30 to 5 wt%, in yet another embodiment 25 to 1 wt%, in yet another embodiment 25 to 3 wt%, alternately 20 to 3 wt%, in yet another embodiment 15 to 1 wt%, in yet another embodiment 10 to 4 wt%; wherein a desirable range may be any combination of any upper wt% limit with any lower wt% limit described herein. Polyethylene

[0034] In some examples, the polyethylene can include ethylene homopolymers and ethylene copolymers. The polyethylene may comprise from 100 to about 80.0 wt%, 99.0 to 85.0 wt%, 99.0 to 87.5 wt%, 99.0 to 90.0 wt%, 99.0 to 92.5 wt%, 99.0 to 95.0 wt%, or 99.0 to 97.0 wt%, of polymer units derived from ethylene 0 to about 20.0 wt%, 0.1 to about 20.0 wt% 1.0 to 15.0 wt%, 0.5 to 12.5 wt%, 1.0 to 10.0 wt%, 1.0 to 7.5 wt%, 1.0 to 5.0 wt%, or 1.0 to 3.0 wt% of polymer units derived from one or more C3 to C20 a-olefm comonomers, preferably C3 to C10 a-olefms, and more preferably C4 to Cx a-olefms, such as hexene and octene. The a-olefm comonomer may be linear or branched, and two or more comonomers may be used, if desired.

[0035] Examples of suitable comonomers include propylene, butene, 1-pentene; 1-pentene with one or more methyl, ethyl, or propyl substituents; 1 -hexene; 1 -hexene with one or more methyl, ethyl, or propyl substituents; 1-heptene; 1-heptene with one or more methyl, ethyl, or propyl substituents; 1 -octene; 1 -octene with one or more methyl, ethyl, or propyl substituents; 1-nonene; 1-nonene with one or more methyl, ethyl, or propyl substituents; ethyl, methyl, or dimethyl-substituted 1-decene; 1-dodecene; and styrene. Particularly suitable comonomers include 1 -butene, 1 -hexene, and 1 -octene, 1 -hexene, and mixtures thereof.

[0036] The polyethylene may have a melt index, I2_.16, according to the test method listed below, of > about 0.10 g/10 min, e.g., > about 0.15 g/10 min, > about 0.18 g/10 min, > about 0.20 g/10 min, > about 0.22 g/10 min, > about 0.25 g/10 min, > about 0.28 g/10 min, or > about 0.30 g/10 min and, also, a melt index (I2_.16) < about 3.00 g/10 min, e.g., < about 2.00 g/10 min, < about 1.00 g/10 min, < about 0.70 g/10 min, < about 0.50 g/10 min, < about 0.40 g/10 min, or < about 0.30 g/10 min. Ranges expressly disclosed include, but are not limited to, ranges formed by combinations any of the above-enumerated values, e.g., about 0.10 to about 0.30, about 0.15 to about 0.25, about 0.18 to about 0.22 g/10 min, etc. In another embodiment, the melt index could be about 0.1 g/10 min to about 30 g/10 min, such as about 20 g/10 min to about 30 g/10 min.

[0037] The polyethylene may have a high load melt index (HLMI) (I21_.6) in accordance with the test method listed below of from 1 to 60 g/10 min, 5 to 40 g/10 min, 5 to 50 g/10 min, 15 to 50 g/10 min, or 20 to 50 g/10 min.

[0038] The polyethylene may have a melt index ratio (MIR), from 10 to 90, from 20 to 45, from 25 to 60, alternatively, from 30 to 55, alternatively, from 35 to 55, and alternatively, from 35 to 50 or 35 to 45. MIR is defined as I21_.6/I2_.16.

[0039] The polyethylene may have a density of about 0.920 g/cm³, about 0.918 g/cm³ , or

> about 0.910 g/cm³, e.g., > about 0.919 g/cm³, > about 0.92 g/cm³, > about 0.930 g/cm³,

> about 0.932 g/cm³. Additionally, the polyethylene may have a density < about 0.945 g/cm³, e.g., < about 0.940 g/cm³, < about 0.937 g/cm³, < about 0.935 g/cm³, < about 0.933 g/cm³, or < about 0.930 g/cm³. Ranges expressly disclosed include, but are not limited to, ranges formed by combinations any of the above-enumerated values, e.g., about 0.919 to about 0.945 g/cm³, 0.920 to 0.930 g/cm³, 0.925 to 0.935 g/cm³, 0.920 to 0.940 g/cm³, etc. Density is determined in accordance with the test method listed below.

[0040] The polyethylene may have a molecular weight distribution (MWD, defined as M_w/M_n) of about 1 to about 12, about 5 to about 10.5 or 11, about 2.5 to about 5.5.

[0041] The polyethylene can have one or more of the following properties: a) a density of from 0.890 g/cm³ to 0.940 g/cm³; b) a melt index (MI) of from 0.1 g/10 min to 30 g/10 min, alternatively, a melt index (MI) of from 0.1 g/10 min to 6 g/10 min; c) a melt index ratio (I21/I2) of from 10 to 90; d) an M_w/M_n of from 2 to 12; e) an M_z/M_w of from 2.5 to 5.0; f) an M_z/M_n of from 10 to 40; and g) a g’_(Vis) of at least 0.900, alternatively, at least 0.930, alternatively, at least 0.940, alternatively, at least 0.950, and alternatively, at least 0.994.

[0042] The polyethylene can be produced by polymerizing ethylene and the optional olefin comonomer in the presence of a transition metal catalyst such as a Ziegler-Natta catalyst (i.e., an organometallic catalyst), a “Philips” type of catalyst (i.e., a supported chromium/chromium oxide catalyst), a metallocene catalyst containing atetravalent transition metal, or combinations thereof. Other suitable catalysts are known in the art. The polymerization process can be performed in solution phase (e.g., when octene is the comonomer) or in a gas phase reactor (e.g., when butene or hexene is the comonomer). The polymerization temperature and pressure can be effective to affect the amount of long chain branching. In some examples, the polyethylene is a linear low-density polyethylene (LLDPE). An exemplary method of producing the LLDPE copolymer can be found in US Patent Application No. 2019/0144575, which is incorporated by reference herein in its entirety.

[0043] An example of a suitable polyethylene L is Exceed™ XP 8656ML, which is commercially available from ExxonMobil.

Cyclic-olefin Copolymer

[0044] As used herein, a “cyclic-olefin copolymer” (COC) is a copolymer comprising 50 wt% or more cyclic olefin or its derived units, the remainder being ethylene and optional a-olefms. The cyclic olefin derived units can be selected from Cs to Cs, or C12, or Ci6, or C20 olefins comprising at least one C5 to Cs cyclic structure, such as, for example, bicyclo compounds such as bicyclo-(2,3,l)-heptene-2. Preferably, the cyclic olefin derived unit can be selected from C5, or Ce to Cs, or C10, or C12, or C20 cyclic-olefin derived units, and more preferably bicyclic olefin derived units which are cyclic olefins containing a bridging hydrocarbon moiety that forms two rings in the overall structure such as in bicyclo-(2,3,l)- heptene-2 (norbomene). Most preferably, the cyclic olefin derived units are selected from norbomene, tetracyclododecene, and substituted versions thereof. The term “cyclic-olefin copolymer” includes a blend of two or more different cyclic-olefin copolymers. In some examples, the cyclic-olefin copolymer can be ethylene norbomene.

[0045] The cyclic-olefin copolymers can be made by any suitable polymerization means. In any embodiment, the cyclic olefin monomer that is combined with ethylene monomers in the polymerization process can be selected from C5 to Cs, or C12, or Ci₆, or C20 olefins comprising at least one C5 to Cs cyclic structure, such as, for example, bicyclo compounds such as bicyclo-(2,3,l)-heptene-2. Preferably, the cyclic olefin can be selected from C5, or G, to Cs, or C10, or C12, or C20 cyclic olefins, and more preferably bicyclic olefins which are cyclic olefins containing a bridging hydrocarbon moiety that forms two rings in the overall structure such as in bicyclo-(2,3,l)-heptene-2 (norbomene). Most preferably, the cyclic olefins used to make the COC's are selected from norbomene, tetracyclododecene, and substituted versions thereof. In order to effect the polymerization process upon combining, as well as combining at a desirable temperature, the components can be combined at a pressure of at least 0.8, or 1, or 2, or 3 MPa; or within a range from 0.8, or 1, or 2, or 3 MPa to 4, or 6, or 8, or 10 MPa. This pressure can come from the addition of the ethylene and/or other gases in the polymerization reactor, and is of course influenced by the temperature of the reactor. The level of ethylene and cyclic olefin can be adjusted to obtain the desired catalytic activity as well as desired level of cyclic olefin comonomer incorporation into the polyethylenes described herein. In any embodiment, the combining of the monomers with catalyst can take place at a reaction temperature, the average temperature within the vessel or reactor used to combine the components to effect polymerization, within a range from 80, or 85, or 90, or 100° to 120, or 130, or 140, or 150°C.

[0046] In some examples, the cyclic-olefin copolymer comprises at least 10, or 20, or 30, or 40, or 50, or 60, or 65, or 70, or 75 wt % cyclic olefin derived units, by weight of the cyclic- olefin copolymer. In some examples, the cyclic-olefin copolymer comprises from 10 to 90 wt%, from 10 to 80 wt%, 10 to 70 wt%, 10 to 60 wt%, 10 to 50 wt%, 10 to 40 wt%, 20 to 90 wt%, from 20 to 80 wt%, 20 to 70 wt%, 20 to 60 wt%, 20 to 50 wt%, 20 to 40 wt%, 30 to 90 wt%, from 30 to 80 wt%, 30 to 70 wt%, 30 to 60 wt%, 30 to 50 wt%, or 30 to 40 wt% cyclic olefin derived units, by weight of the cyclic-olefin copolymer. In some examples, the cyclic- olefin copolymer comprises at least 10, or 20, or 30, or 40, or 50, or 60, or 65, or 70, or 75 mol% cyclic olefin derived units. In some examples, the cyclic-olefin copolymer comprises from 10 to 90 mol%, from 10 to 80 mol%, 10 to 70 mol%, 10 to 60 mol%, 10 to 50 mol%, 10 to 40 mol%, 20 to 90 mol%, from 20 to 80 mol%, 20 to 70 mol%, 20 to 60 mol%, 20 to 50 mol%, 20 to 40 mol%, 30 to 90 mol%, from 30 to 80 mol%, 30 to 70 mol%, 30 to 60 mol%, 30 to 50 mol%, or 30 to 40 mol% cyclic olefin derived units, by weight of the cyclic-olefin copolymer.

[0047] In some examples, the cyclic-olefin copolymer has a Tg value of at least 30, or 40, or 50, or 60, or 65, or 70°C. The cyclic-olefin copolymer can comprise at least 50, or 60, or 65, or 70, or 75 wt% cyclic olefin derived units, by weight of the copolymer. The cyclic-olefin copolymer can have a Tg value within a range from 30, or 40, or 50, or 60, or 65, or 70, or 75, or 80, or 90, or 100°C to 145, or 155, or 160, or 170, or 180°C. The cyclic-olefin copolymer described herein may have a heat of fusion (DH) of less than 120, or 115 J/g, or within a range from 80, or 85, or 90, or 95, or 100, or 105 J/g to 115, or 120 J/g.

[0048] The cyclic-olefin copolymer can also be described by a number of other properties. In some examples, the cyclic-olefin copolymer can have a melt index (MI (190°C/2.16kg)) within a range from 0.05, or 0.10 g/10 min to 1, or 2, or 3, or 4 g/10 min. In some examples, the cyclic-olefin copolymer can have a density within a range from 0.96, or 0.98 g/cm³ to 1, or 1.05, or 1.1 g/cm³. Finally, in some examples, the cyclic-olefin copolymer can have a branching index (gVis) of greater than 0.95, or 0.96, or 0.97, or within a range from 0.95, or 0.96, or 0.97 to 1, or 1.1.

Additives

[0049] Additives may be included in the polyethylene, the cyclic-olefin copolymer, or the blends of the polyethylene and cyclic-olefin copolymer. 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, metal deactivators, stearates, 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 first polyethylene, and the second polyethylene (if present). 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 polyethylene, and the second polyethylene (if present). In some examples, the filler can be calcium carbonate, magnesium carbonate, carbon black, silica, carbon-silica dual-phase filler, clay (layered silicates), lignin, carbon-nanotubes, amorphous fillers, such as glass particle based fillers, starch based fillers, or combinations thereof.

Foaming Agents

[0050] Foaming agents may be included in the polyethylene, the cyclic-olefin copolymer, or the blends of the polyethylene and cyclic-olefin copolymer.

[0051] Foaming agents may generally be divided into two classes: physical foaming agents and chemical foaming agents.

[0052] 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 can be 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. [0053] 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.

[0054] 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.

Sterilization

[0055] In some examples, the polyethylene, the cyclic-olefin copolymer, or the blend of the polyethylene and the cyclic-olefin copolymer can be sterilized by radiation sterilization. Radiation sterilization can use gamma, X-ray or electron radiation, which can deactivate microorganisms such as bacteria, fungi, viruses and spores. In some examples, the polyethylene(s) can be sterilized by ultraviolet (UV) light. Short wavelength UV light can deactivate microorganisms such as bacteria, fungi, viruses and spores. Radiation sterilization or UV sterilization can occur to one or more of the polyethylene, the cyclic-olefin copolymer, the blend of the polyethylene and the cyclic-olefin copolymer, the filament, and the 3D printed article.

Blends

[0056] In one or more embodiments, the blends described herein comprise the polyethylene, the cyclic-olefin copolymer, optionally additives, and optionally foaming agents and can be formed using any suitable means and are typically blended to yield an intimately mixed composition or a uniform mixture. The blends described herein can be formed using conventional equipment and methods, such as by dry blend using a tumbler, double-cone blender, ribbon blender, or other suitable blender and subsequently subjected to melt mixing in a mixer, or by mixing the components together directly in a mixer, such as, for example, a Banbury mixer, a Haake mixer, a Brabender internal mixer, or a single or twin-screw extruder, which may include a compounding extruder and a side-arm extruder. In other embodiments, the polyethylene and the cyclic-olefin copolymer are blended by a combination of approaches, for example a tumbler followed by an extruder. Additionally, additives and/or foaming agents can be included in the blend, in one or more components of the blend, and/or in a product formed from the blend, such as a filament, as desired.

[0057] In yet more embodiments, the polyethylene and the cyclic-olefin copolymer can be blended using a “master batch” approach. The mixing step can take place as part of an additive manufacturing process to fabricate 3D articles, such as in the melting chamber on a 3D printing machine.

[0058] In a preferred aspect of the invention, the polyethylene and the cyclic-olefin copolymer along with additives and/or foaming agents (if present) are “melt blended” in an apparatus such as an extruder (single or twin screw) or batch mixer. Preferably, the screw of the melt extruder has multiple sections along the length of the barrel including the feed, the compression, and the metering sections. The raw material can be fed from the hopper directly into the feed section. The polymer is mainly melted in the compression zone. The polymers exist in a molten state when entering the metering section, which has the main function of reducing the pulsating flow to ensure a uniform delivery rate through the die. Preferably the temperatures of all of the barrels can be independent and can be accurately controlled in a range from 30°C to 250°C. The extruder die is used to shape the molten strand as it leaves the extruder into filament. In one preferred embodiment, the temperature can be increased from about 150°C in the feed section to about 210°C in the metering section of the barrel. In this manner, filaments can be formed from the blend that can have a diameter of about 2.40 mm to about 3.00 mm, preferably about 2.65 mm to about 3.00 mm, and more preferably about 2.75 mm to about 3.00 mm. A preferred method of blending is to include the final stage of blending as part of the filament fabrication step, such as in the extruder used to melt and convey the composition to a printing nozzle (or a die).

[0059] In another aspect of the invention, the polymer components can be blended in solution by any suitable means, by using a solvent that dissolves both components to a significant extent. The blending may occur at any temperature or pressure where the polymers remain in solution. Preferred conditions include blending at high temperatures, such as 20°C or more, preferably 30°C or more over the peak melting point of the polyethylene. Such solution blending could be particularly useful in processes where the polymer components are made by solution process and the mixing step is part of the finishing train, rather than added to the dry polymer in another blending step altogether. Such solution blending could also be particularly useful in processes where the polyethylene is made in a bulk or high pressure process where the both the polymers are soluble in the monomer.

[0060] Rheological properties of the blend can play a key role in controlling and improving the coalescence of the deposited beads on the obj ect being printed. The molten viscosity should be high enough to provide structural support and low enough to enable extrusion. The blend preferably has a complex viscosity at a frequency of 0.1 rad/sec and a temperature of 190°C within the range of from 1,000 or 3,000 or 5,000 or 8,000, or 10,000 or 15,000 Pa.s to 20,000 or 50,000 or 100,000 or 500,000 or 1,000,000 Pa.s. The blend preferably has a complex viscosity at a frequency of 100 rad/sec and a temperature of 190°C within the range of from 50 or 100 or 200 or 500 Pa.s to 5,000 or 8,000 or 10,000 or 15,000 Pa.s.

[0061] In one embodiment, the blend has significant shear induced viscosity thinning. Shear thinning is characterized by the decrease of the complex viscosity with increasing shear rate. One way to quantify the shear thinning is to use a ratio of complex viscosity at a frequency of 0.1 rad/s to the complex viscosity at a frequency of 100 rad/s. Preferably, the complex viscosity ratio of the blend is 5 or more, more preferably 10 or more, even more preferably 15 or more when the complex viscosity is measured at 190°C using a small amplitude oscillatory shear (SAOS).

[0062] In at least one embodiment, the melt strength of the blend may be from about 1 cN to about 540 cN, about 1 cN to about 50 cN, about 1 cN to about 25 cN, about 3 cN to about 15 cN, about 4 cN to about 12 cN, about 5 cN to about 10 cN, or about 5 cN to about 15 cN, when measured at 190°C. In some embodiments, the blend has a melt strength of at least about 5 cN, at least about 10 cN, or at least about 15 cN, and about 30 up to about 20 cN, when measured at 190°C. The melt strength of a blend at a particular temperature may be determined with a Gottfert Rheotens Melt Strength Apparatus. To determine the melt strength, a composition (e.g., of a film) melt strand extruded from the capillary die is gripped between two counter-rotating wheels on the apparatus. The take-up speed is increased at a constant acceleration of about 12 mm/s². The maximum pulling force (in the unit of cN) achieved before the strand breaks or starts to show draw-resonance is determined as the melt strength. The temperature of the rheometer is set at 190°C. The capillary die has a length of about 30 mm and a diameter of about 2 mm. The film melt is extruded from the die at a speed of about 10 mm/s. The distance between the die exit and the wheel contact point should be about 122 mm. [0063] The polymers suitable for use in the present invention can be in any physical form when used for filament fabrication. In one embodiment, reactor granules, defined as the granules of polymer that are isolated from the polymerization reactor prior to any processing procedures, are used to make blends of the invention. The reactor granules typically have an average diameter of from 50 pm to 10 mm in one embodiment, and from 10 pm to 5 mm in another embodiment. In another embodiment, the polymer is in the form of pellets, such as, for example, having an average diameter of from 1 mm to 10 mm that are formed from melt extrusion of the reactor granules.

[0064] The blend can have a crystallization temperature (Tc) of at least 100, or 102°C, or within a range from 100, or 102°C to 106, or 110°C.

[0065] The blend of the polyethylene and the cyclic-olefin copolymer or any article made therefrom can have rods having an average length of at least 1, or 2, or 4, or 5 pm, and at least 5, or 10, or 20, or 30 nm in average diameter; or an average length within a range from 1, or 2, or 4, or 5 pm, to 8, or 10, or 20, or 50 pm, and average diameter within a range from 5, or 10, or 20, or 30 nm to 60, or 80, or 100, or 120 nm.

Additive Manufacturing Processes and Devices

[0066] 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 3D numeric coordinates of the entire configuration of the component including both external and internal surfaces. The model can include a number of successive 2D cross-sectional slices that together form the 3D component.

[0067] As such, additive manufacturing systems can be used to print or otherwise build three-dimensional ("3D") parts from digital representations of the 3D parts using one or more additive manufacturing techniques, such as fused filament fabrication.

[0068] At an initial stage, the digital representation of the 3D 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.

[0069] 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.

[0070] The 3D printing filament used in the process can include the blend of the polyethylene and cyclic-olefin copolymer as described above. The polyethylene, cyclic-olefin copolymer, 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 3D filaments can be used, such as the process described in the examples below.

[0071] 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.

[0072] 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.

[0073] 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 3D 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 3D structure.

[0074] 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.

[0075] 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.

[0076] 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. [0077] 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.

[0078] 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.

[0079] 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.

[0080] When 3D printing thermoplastic polymers using additive manufacturing, the adhesion between the first printed layer and the printing bed can be crucial, since it provides the foundation to the subsequent layers. Inadequate adhesion can result in poor printing quality or destroyed bed surfaces. The optimal adhesion of the printed sample to the printing bed can be achieved by heating the printing bed at temperatures above glass transition temperature (Tg) of the filament material. Increasing the temperature above the filament’s Tg leads to a reduction of the surface tension between the printing bed and the printing material and to a larger contact area that ultimately causes better adhesion between the bed and the filament. For 3D printing polyolefins, the build plate temperature range can be any temperature above Tg, and below Tm or degradation temperature (whatever is lower) of the printing filament. In some examples, the extrusion temperature is from 100 to 250°C, preferred from 120-240°C, more preferred froml55 to 230°C. The Extruder screw rotation speed can be from 30 to 50 RPM, preferred from 35 to 45 RPM, more preferred from 38 to 40 RPM.

[0081] The 3D printer nozzle temperature can be above the melting temperature and below the degradation temperature of the printing filament.

[0082] To prevent warping, 3D printed parts can have good adhesion to the build plate. Physical adjustments to ensure good adhesion between 3D printed parts and build plate can include one or more of the following:

(1) Using a heated build plate. When printing polymers, the build plate temperature can be around 25°C.

(2) Applying an adhesive to the build plate. The commonly used adhesives for polyolefin include commercially available printing adhesive solution, or polyolefin based tapes.

(3) Ensure the build plate is leveled correctly. It can be important that the first print layer of a print is pressed firmly onto the glass plate, to allow it to bond properly. If the distance between the nozzle and build plate is too wide, the material can easily become loose.

(4) Ensure build plate surface is smooth and clean.

(5) Materials that require a high build plate temperature requires an isothermal printing environment. Cooler airflows from the environment can cause adhesion problems, and in extreme cases, may cause the print to separate from the build plate.

[0083] Software adjustments to help improve adhesion can include: 1) Use a “brim”. Placing a single-layer-thick flat area around the object can creating a larger adhesion surface. Print warping can be minimized by this. After printing, the brim can be removed easily.

2) Use a raft. For some materials or models, a brim might not be enough to prevent warping. In these instances, using a raft can be advisable. A raft can add a thick grid between the model and the build plate, ensuring that the heat is distributed equally. It is particularly useful when the bottom of a model is not completely flat, or when printing with industrial materials.

3) Two important settings (relating to the first layer) that influence adhesion are the initial layer height and initial layer speed. In some cases, a thicker initial layer can make adhesion easier, as build plate calibration is not as critical. It is important not to set the initial layer speed too high, as the material may attach to the nozzle and get dragged around with it, instead of remaining fixed to the build plate. Adjusting initial layer settings to use a low initial layer speed can ensure that the material has enough time to properly adhere to the build plate. For polyolefins, first layer printing speed can be around 6 mm/s.

4) Cooling can be one of the main causes of warping. Material contracts when cooling, and can cause the material to pull on itself. Materials can be cooled properly before the next layer is added, but excessive cooling should be avoided to ensure a smooth, warp-free print. For polyolefins, the recommended cooling can vary material by material.

[0084] 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 3D printed component can be personal protective devices, medical facemasks, masks, mask components, tubing, goggles, shoes, hats or ventilator components.

[0085] In some examples, the 3-D component can have a Notch Izod Impact at 29°C of at least 10 Ft*lbf/in, or 11 Ft*lbf/in, or 12 Ft*lbf/in or 13 Ft*lbf/in, or 14 Ft*lbf/in, or 15 Ft*lbf/in. In some examples, the 3-D component can have a Notch Izod Impact at 29°C of from 10 Ft*lbf/in to 20 Ft*lbf/in, from 10 Ft*lbf/in to 18 Ft*lbf/in, from 12 Ft*lbf/in to 20 Ft*lbf/in, from 12 Ft*lbf/in to 18 Ft*lbf/in, from 12 Ft*lbf/in to 17 Ft*lbf/in, from 13 Ft*lbf/in to 20 Ft*lbf/in, from 13 Ft*lbf/in to 18 Ft*lbf/in, from 13 Ft*lbf/in to 17 Ft*lbf/in, from 14 Ft*lbf/in to 20 Ft*lbf/in, from 14 Ft*lbf/in to 18 Ft*lbf/in, or from 14 Ft*lbf/in to 17 Ft*lbf/in.

[0086] In some examples, the 3-D component can have a Flex Modulus of at least 100 MPa, or 150 MPa, or 175 MPa or 200 MPa, or 225 MPa, or 250 MPa. In some examples, the 3-D component can have a Flex Modulus of from 100 MPa to 400 MPa, from 100 MPa to 300 MPa, from 100 MPa to 275 MPa, from 175 MPa to 400 MPa, from 175 MPa to 300 MPa, from 175 MPa to 275 MPa, from 200 MPa to 400 MPa, from 200 MPa to 300 MPa, from 200 MPa to 275 MPa, from 225 MPa to 400 MPa, from 225 MPa to 300 MPa, from 225 MPa to 275 MPa. [0087] In some examples, the 3-D component can have a Strain at Break of at least 200%, or 250%, or 300% or 350%, or 400%, or 450%. In some examples, the 3-D component can have a Strain at Break of from 200% to 600%, from 200% to 550%, from 200% to 500%, from 300% to 600%, from 300% to 550%, from 300% to 500%, from 350% to 600%, from 350% to 550%, from 350% to 500%, from 400% to 600%, from 400% to 550%, or from 400% to 500%. [0088] In some examples, the 3-D component can have a Modulus (1% Secant) of at least 100 MPa, or 150 MPa, or 175 MPa or 200 MPa, or 225 MPa, or 250 MPa or 300 MPa or 350 MPa or 400 MPa or 430 MPa. In some examples, the 3-D component can have a Modulus (1% Secant) of from 100 MPa to 600 MPa, from 100 MPa to 500 MPa, from 100 MPa to 475 MPa, from 200 MPa to 600 MPa, from 200 MPa to 500 MPa, from 200 MPa to 475 MPa, from 300 MPa to 600 MPa, from 300 MPa to 500 MPa, from 300 MPa to 475 MPa, from 400 MPa to 600 MPa, from 400 MPa to 500 MPa, or from 400 MPa to 475 MPa.

[0089] In some examples, the 3-D component can have a Young’s Modulus of at least 100 MPa, or 150 MPa, or 175 MPa or 200 MPa, or 225 MPa, or 250 MPa or 300 MPa or 350 MPa or 400 MPa or 450 MPa. In some examples, the 3-D component can have a Modulus (1% Secant) of from 100 MPa to 600 MPa, from 100 MPa to 500 MPa, from 100 MPa to 480 MPa, from 200 MPa to 600 MPa, from 200 MPa to 500 MPa, from 200 MPa to 480 MPa, from 300 MPa to 600 MPa, from 300 to 500 MPa, from 300 MPa to 480 MPa, from 400 MPa to 600 MPa, from 400 MPa to 500 MPa, or from 400 MPa to 480 MPa.

[0090] In some examples, the 3-D component can have a Tensile Stress at Yield of less than 20 MPa, 18 MPa, 16 MPa, 14 MPa, 12 MPa, or 10 MPa. In some examples, the 3-D component can have a Tensile Stress at Yield of from 6 MPa to 15 MPa, from 6 MPa to 14 MPa, from 6 MPa to 13 MPa, from 8 MPa to 15 MPa, from 8 MPa to 14 MPa, from 8 MPa to 13 MPa, 9 to 15 MPa, from 9 MPa to 14 MPa, from 9 MPa to 13 MPa, 10 MPa to 15 MPa, from 10 MPa to 14 MPa, or from 10 MPa to 13 MPa.

[0091] In some examples, the 3-D component can have a Tensile Stress at Break of at least 10 MPa, or 12 MPa, or 14 MPa or 16 MPa, or 18 MPa. In some examples, the 3-D component can have a Tensile Stress at Break of from 10 MPa to 30 MPa, from 10 MPa to 25 MPa, from 10 MPa to 20 MPa, from 12 MPa to 30 MPa, from 12 MPa to 25 MPa, from 12 MPa to 20 MPa, from 14 MPa to 30 MPa, from 14 MPa to 25 MPa, or from 14 MPa to 20 MPa.

[0092] This invention further relates to:

1. A process for making a three-dimensional object using an additive manufacturing process, comprising: preparing a blend comprising polyethylene and a cyclic-olefin copolymer; extruding the composition 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 fluid bead of the filament is dispensed out of the nozzle onto a heated build plate.

3. The process of paragraph 1 or paragraph 2, wherein the heated build plate has an adhesive applied to a surface of the heated build plate.

4. The process of any of paragraphs 1 to 3, wherein the polyethylene has a g’_viS of at least 0.95.

5. The process of any of paragraphs 1 to 4, wherein the polyethylene has a density of less than 0.94 g/cm³.

6. The process of any of paragraphs 1 to 5, wherein the cyclic-olefin copolymer has a glass transition temperature of at least 30°C.

7. The process of any of paragraphs 1 to 6, wherein the cyclic-olefin copolymer has a glass transition temperature from 30°C to 180°C.

8. The process of any of paragraphs 1 to 7, wherein the blend comprises from about 25 wt% to about 99 wt% of the polyethylene and from 1 wt% to 25 wt% of the cyclic-olefin copolymer based on a total weight of the polyethylene and the cyclic-olefin copolymer.

9. The process of any of paragraphs 1 to 8, wherein the cyclic-olefin copolymer is ethylene norbomene. 10. The process of paragraph 9, wherein the ethylene norbomene comprises from 10 to 40 mol% norbomene.

11. A process for making a filament, comprising: preparing a blend comprising polyethylene and a cyclic-olefin copolymer; extruding the composition to make a filament, wherein the filament has a diameter from about 0.01 mm to about lm; and collecting the filament on a spool.

12. The process of paragraph 11 , wherein the spool collects the filament at a rate from about 0.001 m/s to about 0.5 m/s.

13. The process of paragraph 11 or paragraph 12, wherein the fluid bead of the filament is dispensed out of the nozzle onto a heated build plate.

14. The process of any of paragraphs 11 to 13, wherein the heated build plate has an adhesive applied to a surface of the heated build plate.

15. The process of any of paragraphs 11 to 14, wherein the polyethylene has a g’_viS of at least 0.95.

16. The process of any of paragraphs 11 to 15, wherein the polyethylene has a density of less than 0.94 g/cm³.

17. The process of any of paragraphs 11 to 16, wherein the cyclic-olefin copolymer has a glass transition temperature of at least 30°C.

18. The process of any of paragraphs 11 to 17, wherein the cyclic-olefin copolymer has a glass transition temperature from 30°C to 180°C.

19. The process of any of paragraphs 11 to 18, wherein the blend comprises from about 25 wt% to about 99 wt% of the polyethylene and from 1 wt% to 25 wt% of the cyclic-olefin copolymer based on a total weight of the polyethylene and the cyclic-olefin copolymer.

20. The process of any of paragraphs 11 to 19, wherein the cyclic-olefin copolymer is ethylene norbomene. 21. The process of paragraph 20, wherein the ethylene norbomene comprises from 10 to 40 mol% norbomene.

22. A filament comprising, a blend comprising polyethylene and a cyclic-olefin copolymer, wherein the filament has a diameter from about 1 mm to about 3 mm.

23. The filament of paragraph 22, wherein the diameter of the filament changes less than 0.1 mm per meter of the filament.

24. The process of paragraph 22 or paragraph 23, wherein the fluid bead of the filament is dispensed out of the nozzle onto a heated build plate.

25. The process of any of paragraphs 22 to 24, wherein the heated build plate has an adhesive applied to a surface of the heated build plate.

26. The process of any of paragraphs 22 to 25, wherein the polyethylene has a g’_viS of at least 0.95.

27. The process of any of paragraphs 22 to 26, wherein the polyethylene has a density of less than 0.94 g/cm³.

28. The process of any of paragraphs 22 to 27, wherein the cyclic-olefin copolymer has a glass transition temperature of at least 30°C.

29. The process of any of paragraphs 22 to 28, wherein the cyclic-olefin copolymer has a glass transition temperature from 30°C to 180°C.

30. The process of any of paragraphs 22 to 29, wherein the blend comprises from about 25 wt% to about 99 wt% of the polyethylene and from 1 wt% to 25 wt% of the cyclic-olefin copolymer based on a total weight of the polyethylene and the cyclic-olefin copolymer.

31. The process of any of paragraphs 22 to 30, wherein the cyclic-olefin copolymer is ethylene norbomene.

32. The process of paragraph 31 , wherein the ethylene norbomene comprises from 10 to 40 mol% norbomene.

33. An article printed using the process of paragraph 1. 34. The article of paragraph 33 wherein the article is a mask or mask component.

EXAMPLES Test Methods

Dynamic Mechanical Analysis (DMA)

[0093] The glass transition temperature (T_g) is measured using dynamic mechanical analysis. This test provides information about the small-strain mechanical response of a sample as a function of temperature over a temperature range that includes the glass transition region and the visco-elastic region prior to melting. Specimens are tested using a commercially available DMA instrument (e.g., TA Instruments DMA 2980 or Rheometrics RSA) equipped with a dual cantilever test fixture. The specimen is cooled to -130°C then heated to 60°C at a heating rate of 2°C/min while subjecting to an oscillatory deformation at 0.1% strain and a frequency of 1 rad/sec. The output of these DMA experiments is the storage modulus (E’) and loss modulus (E”). The storage modulus measures the elastic response or the ability of the material to store energy, and the loss modulus measures the viscous response or the ability of the material to dissipate energy. The ratio of E"/E', called Tan-delta, gives a measure of the damping ability of the material; peaks in Tan-delta are associated with relaxation modes for the material. T_g is defined to be the peak temperature associated with the b-relaxation mode, which typically occurs in a temperature range of -80 to +20°C for polyolefins. In a hetero phase blend, separate b-relaxation modes for each blend component may cause more than one T_g to be detected for the blend; assignment of the T_g for each component are preferably based on the T_g observed when the individual components are similarly analyzed by DMA (although slight temperature shifts are possible).

Gel Permeation Chromatography (GPC)

[0094] Unless otherwise indicated, the distribution and the moments of molecular weight (Mw, Mn, Mz, Mw/Mn, etc.), the comonomer content and the branching index (g is) 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 2,700 cm ¹ to about 3,000 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-tri chlorobenzene (TCB) (from Sigma- Aldrich) comprising -300 ppm antioxidant butylated hydroxytoluene (BHT) is 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 is contained in an oven maintained at ~145°C. A given amount of sample is 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 is dissolved in the instrument with -8 mL added TCB solvent at ~160°C with continuous shaking. The sample solution concentration is 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: log (K_pS/K) a_PS + 1 l^{0gM =} + 1 ⁺! n^{~l0g MK} 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 in the published in literature (Sun, T. et al. Macromolecules 2001, V.34, pg. 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, a = 0.695 and K = 0.000579 for other 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.

[0095] The comonomer composition is determined by the ratio of the IR5 detector intensity corresponding to CEE and CEE 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 1,000 total carbons (CH3/IOOOTC) as a function of molecular weight. The short-chain branch (SCB) content per 1,000TC (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, Ce, Cs, and so on co-monomers, respectively: w2 = / * SCB/1000TC

[0096] The bulk composition of the polymer from the GPC-IR and GPC-4D analyses is obtained by considering the entire signals of the CTb and CH2 channels between the integration limits of the concentration chromatogram. First, the following ratio is obtained

Area of CH₃ signal within integration limits

Bulk IR ratio =

Area of CH₂ signal within integration limits ^'

[0097] Then the same calibration of the CTb and CFh signal ratio, as mentioned previously in obtaining the CH3/1000TC as a function of molecular weight, is applied to obtain the bulk CH3/1000TC. A bulk methyl chain ends per lOOOTC (bulk CH3end/1000TC) is obtained by weight-averaging the chain-end correction over the molecular-weight range. Then w2b = f * bulk CH3/1000TC 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. [0098] 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:

4p²h² (dn/dc)²

K o l⁴N_A 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. [0099] 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, h₈, 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]= q_s/c. where c is concentration and is determined from the IR5 broadband channel output. The viscosity MW at each point is calculated as M = K_psM^aps+l /[h] , where a_ps is 0.67 and K_ps is 0.000175.

[0100] 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.

Wav

The branching index g'_vis is defined as g'_vls = — , where M_v is the viscosity-average

KM: 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, a = 0.695 and K = 0.000579 for other 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) [0101] 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. Under 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 maj or 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.

Other Test methods

[0102] Additional test methods include the following.

Example 1 LLDPE/Cvclic Olefin Copolymer Filament fabrication description

[0103] 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

[0104] All Fused Deposition Modeling (FDM) specimens were fabricated with an Airw olfSD" 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 3D 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 3D printer, and 3D 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

[0105] 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 tests.

[0106] Tensile and flexural 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. All materials are injection molded or 3D printed into IS037 Type 3 bar dimensions. Tensile measurements use ASTM D638-14 protocol, with stretching speed of 1.0 mm/min and span of 30 mm. Flexural measurements use ASTM D790-17 protocol.

Table 2

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

Claims

CLAIMS: What is claimed is:

1. A process, comprising: preparing a blend comprising polyethylene and a cyclic-olefin copolymer; and extruding the composition to make a filament.

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 the three- dimensional object.

3. The process of claim 2, wherein the dispensing includes dispensing the fluid bed out of a nozzle on to a heated build plate that has an adhesive applied to a surface of the heated build plate.

4. The process of any preceding claim, wherein the polyethylene has a g’ _vis of at least 0.95.

5. The process of any preceding claim, wherein the polyethylene has a density of less than 0.94 g/cm³.

6. The process of any preceding claim, wherein the cyclic-olefin copolymer has a glass transition temperature of at least 30°C.

7. The process of any preceding claim, wherein the cyclic-olefin copolymer has a glass transition temperature from 30°C to 180°C.

8. The process of any preceding claim, wherein the blend comprises from about 25 wt% to about 99 wt% of the polyethylene and from 1 wt% to 25 wt% of the cyclic-olefin copolymer based on a total weight of the polyethylene and the cyclic-olefin copolymer.

9. The process of any preceding claim, wherein the cyclic-olefin copolymer is ethylene norbomene.

10. The process of claim 9, wherein the ethylene norbomene comprises from 10 to 40 mol% norbomene.

11. The process of any preceding claim, wherein the filament has a diameter from about 0.01 mm to about 1 m, wherein the method further comprises collecting the filament on a spool.

12. The process of claim 11, wherein the spool collects the filament at a rate from about 0.001 m/s to about 0.5 m/s.

13. A filament comprising, a blend comprising polyethylene and a cyclic-olefin copolymer, wherein the filament has a diameter from about 1 mm to about 3 mm.

14. The filament of claim 13, wherein the diameter of the filament changes less than

0.1 mm per meter of the filament.