WO2019063740A1

WO2019063740A1 - Method for manufacturing a three-dimensional object using polyamide based support material

Info

Publication number: WO2019063740A1
Application number: PCT/EP2018/076365
Authority: WO
Inventors: Sergio Mastroianni; Stéphane JEOL; Marie-Laure MICHON
Original assignee: Rhodia Operations; Solvay Specialty Polymers Usa, Llc
Priority date: 2017-09-28
Filing date: 2018-09-27
Publication date: 2019-04-04

Abstract

The invention pertains to a method for manufacturing a three-dimensional object with an additive manufacturing system, such as an extrusion-based additive manufacturing system, a selective laser sintering system, and/or an electrophotography-based additive manufacturing system, comprising providing a support material comprising more than 50 % wt. of a polyamide comprising from 60 mole percent to 100 mole percent of recurring units represented by formula (I): - C(O)-A-C(O)-NH-X-NH- (I) wherein A represents a divalent hydrocarbon based group chosen from saturated or unsaturated aliphatics, saturated or unsaturated cycloaliphatics, aromatics comprising at least 5 carbon atoms, arylaliphatics and alkylaromatics; and X represents a divalent group of formula (II) or (III).

Description

Method for manufacturing a three-dimensional object using polyamide based support material

Related Application

[0001 ] This application claims priority to U.S. provisional application No. 62/564,603 filed on September 28, 2017, the whole content of this application being incorporated herein by reference for all purposes.

Technical Field

[0002] The present disclosure relates to a method for manufacturing a three- dimensional object with an additive manufacturing system.

Background Art

[0003] Additive manufacturing systems are used to print or otherwise build 3D parts from digital representations of the 3D parts using one or more additive manufacturing techniques. Examples of commercially available additive manufacturing techniques include extrusion-based techniques, jetting, selective laser sintering, powder/binder jetting, electron-beam melting, and stereolithography processes. For each of these techniques, the digital representation of the 3D part is initially sliced into multiple horizontal layers. For each sliced layer, a tool path is then generated, which provides instructions for the particular additive manufacturing system to print the given layer.

[0004] For example, in an extrusion-based additive manufacturing system, a 3D part may be printed from a digital representation of the 3D part in a layer-by-layer manner by extruding a flowable part material. The part material is extruded through an extrusion tip carried by a print head of the system, and is deposited as a sequence of roads on a platen in an x-y plane. The extruded part material fuses to previously deposited part material, and solidifies upon a drop in temperature. The position of the print head relative to the substrate is then incremented along a z-axis (perpendicular to the x-y plane), and the process is then repeated to form a 3D part resembling the digital representation. An example of extrusion-based additive manufacturing system starting from filaments is called Fused Filament Fabrication (FFF) or Fused Deposition Modeling (FDM).

[0005] In fabricating 3D parts by depositing layers of a part material, supporting layers or structures are typically built underneath overhanging portions or in cavities of 3D parts under construction, which are not supported by the part material itself. A support structure may be built utilizing the same deposition techniques by which the part material is deposited. The host computer generates additional geometry acting as a support structure for the overhanging or free-space segments of the 3D part being formed, and in some cases, for the sidewalls of the 3D part being formed. The support material adheres to the part material during fabrication, and is removable from the completed 3D part when the printing process is complete.

[0006] Generally, soluble/leachable materials are used as support materials,

enabling hence dissolving the support parts from the final 3D part, once the same is built, so that a soak and rinse post-processing is effective in recovering the part.

[0007] Within this scenario, WO-A-99/60508 (STRATASYS, INC.) discloses the use of poly(2-ethyl-2-oxazoline) (PEO) materials of formula:

as support materials for a fused filament forming technique, including removal thereof through soaking and rinsing. These PEO materials may be compounded with polyethylene glycol plasticizers, and plasticized

formulations maybe further formulated notably with polyamides, in amounts not exceeding 35 % wt, the said polyamides being possibly Nylon 12, and amorphous copolymers of terephthalic acid, isophthalamide and

hexamethylenediamine, amorphous Nylon 6/Nylon 12 copolymer, and the like. [0008] Similarly, US-A-2015/0028523 (STRATASYS, INC.) discloses the use of a polyglycolic acid (PGA) support material for use in an additive manufacturing system, which can be removed by soaking in an aqueous medium. According to certain embodiment's, the PGA may comprise connected blocks of polyamide type, of aliphatic or aromatic type, in particular when to be used in association with polyamide part materials.

[0009] Nevertheless, choice of water-soluble polymers is relatively limited; water- soluble polymer compounds may be inadequate for supporting printing of certain polymers that require processing temperatures up to 300 °C, and in some cases soaking/rinsing detaching technique remains nevertheless quite burdensome, at least in that it requires post-treatment of significant amounts of waste waters, for disposal and/or recovering of water-soluble support polymer. In other cases, the use of soluble polymers as support material is the only way to generate hollow structures of the part material.

[0010] In fabricating 3D parts in association with part materials such as amorphous polymers having a glass transition temperature, as determined according to ASTM E1356, of from 100 to 180 °C, and semi-crystalline polymers having a melting point, as determined according to ASTM D3418, of from 100 °C to 260 °C and the like, support materials are required to provide vertical and/or lateral support in operating conditions required for the said part materials, and shall not soften too much under the operating conditions: deformation would otherwise render them ineffective as support structure materials.

Nevertheless, there is a continuous quest for improved support materials simultaneously responding to the requirements for being used as support materials in additive manufacturing techniques, in particular in combination with part materials requiring processing temperatures up to 300 °C, and which can be easily removed from the 3D shaped parts via easy techniques.

Summary of invention

[001 1] An aspect of the present disclosure is directed to a method for manufacturing a three-dimensional object with an additive manufacturing system, such as an extrusion-based additive manufacturing system, a selective laser sintering system, and/or an electrophotography-based additive manufacturing system, comprising providing a support material comprising more than 50 % wt. of a polyamide comprising from 60 mol.% to 100 mol.% of recurring units represented by formula (I):

- C(O)-A-C(O)-NH-X-NH- (I) wherein

A represents a divalent hydrocarbon based group chosen from saturated or unsaturated aliphatics, saturated or unsaturated cycloaliphatics, aromatics comprising at least 5 carbon atoms, arylaliphatics and alkylaromatics; and X represents a divalent group of formula (II) or (III).

[0012] The method also includes providing a part material, printing layers of a

support structure from the provided support material, and printing layers of the three-dimensional object from the provided part material in coordination with the printing of the layers of the support structure to provide an assembly of support structure and three-dimensional object, wherein at least a portion of the printed layers of the support structure support the printed layers of the three-dimensional object.

[0013] The method further includes removing at least a portion of the support

structure from the assembly so as to obtain the three-dimensional object.

[0014] The use of the support material of the present invention enables printing part materials from engineering plastics requiring processing temperatures of up to 300°C, and provides for support parts undergoing, upon exposure to moisture, sufficient swelling, deformation or even complete dissolution, to enable effective and prompt detaching from the printed part. Description of embodiments

[0015] Polyamides of the present invention comprise from 60 mol.% to 100 mol.% of recurring units of formula (I):

- C(O)-A-C(O)-NH-X-NH- (I), wherein

[0016] Polyamides of the present invention comprise preferably from 80 mol. % to 100 mol. % of recurring units of formula (I), more preferably from 90 mol. % to 100 mol. % of recurring units of formula (I). Still more preferably, polyamides of the present invention have 100 mol. % of recurring of formula

(I).

[0017] Preferably, A represents a linear or branched alkylene group having from 1 to 6 carbon atoms.

[0018] More preferably, A represents a linear alkylene group having from 1 to 6

carbon atoms.

[0019] Even more preferably, A represents a linear alkylene group having from 2 to 5 carbon atoms.

[0020] Most preferred is employing in the method according to the present invention a polyamide wherein A represents a linear alkylene group having 4 carbon atoms and X represents the group of formula (III). Such polyamide is hereinafter referred to as "PA THF6".

[0021] The polyamide of the present invention is, for example, a condensation

product of at least one mixture (M1 ) comprising at least a diacid [acid (DA)] (or derivative thereof) and at least a diamine [amine (NN)] (or derivatives thereof).

[0022] Acid (DA) derivatives include notably salts, anhydride, esters and acid

halides, able to form amide groups; similarly, amine (NN) derivatives include notably salts thereof, equally able to form amide groups.

[0023] As disclosed above in the context of defining group A of formula (I), said acid (DA) can be selected from one or more of the group consisting of saturated and unsaturated aliphatic acid, saturated and unsaturated cycloaliphatic acid, aromatic acid comprising at least 5 carbon atoms, arylaliphatic acid and alkylaromatic acid, each thereof comprising two reactive carboxylic acid groups. For the purpose of the present invention, a dicarboxylic acid is considered as "aromatic" when it comprises one or more than one aromatic group.

[0024] Non limitative examples of aromatic, arylaliphatic and alkylaromatic acids are phthalic acids, including isophthalic acid (IA), and terephthalic acid (TA), 2,5- pyridinedicarboxylic acid, 2,4-pyridinedicarboxylic acid, 3,5- pyridinedicarboxylic acid, 2,2-bis(4-carboxyphenyl)propane, bis(4- carboxyphenyl)methane, 2,2-bis(4-carboxyphenyl)hexafluoropropane, 2,2- bis(4-carboxyphenyl)ketone, 4,4'-bis(4-carboxyphenyl)sulfone, 2,2-bis(3- carboxyphenyl)propane, bis(3-carboxyphenyl)methane, 2,2-bis(3- carboxyphenyl)hexafluoropropane, 2,2-bis(3-carboxyphenyl)ketone, bis(3- carboxyphenoxy)benzene, naphthalene dicarboxylic acids, including 2,6- naphthalene dicarboxylic acid, 2,7-naphthalene dicarboxylic acid, 1 ,4- naphthalene dicarboxylic acid, 2,3-naphthalene dicarboxylic acid, 1 ,8- naphthalene dicarboxylic acid and biphenyl-4,4'-dicarboxylic acid.

[0025] Among aliphatic acids, mention can be notably made of oxalic acid (HOOC- COOH), malonic acid (HOOC-Ch -COOH), succinic acid [HOOC-(CH₂)₂- COOH], glutaric acid [HOOC-(CH₂)3-COOH], 2-methyl-glutaric acid

[HOOC-CH(CH₃)-(CH₂)2-COOH], 2,2-dimethyl-glutaric acid

[HOOC-C(CH₃)2-(CH₂)2-COOH], adipic acid [HOOC-(CH₂)₄-COOH],

2,4,4-trimethyl-adipic acid [HOOC-CH(CH₃)-CH₂-C(CH₃)2- CH₂-COOH], pimelic acid [HOOC-(CH₂)₅-COOH], suberic acid [HOOC-(CH₂)₆-COOH], azelaic acid [HOOC-(CH₂)₇-COOH], sebacic acid [HOOC-(CH₂)₈-COOH], undecanedioic acid [HOOC-(CH2)9-COOH], dodecandioic acid [HOOC-(CH₂)io-COOH], tridecanedioic acid [HOOC-(CH₂)i i-COOH], tetradecandioic acid [HOOC-(CH₂)i2-COOH], octadecandioic acid [HOOC-

[0026] Cycloaliphatic acids which can be used include cycloaliphatic-group

containing acids, including notably 1 ,4-cyclohexane dicarboxylic acid, 1 ,3- cyclohexane dicarboxylic acids, as cis or trans diastereoisomers, possibly in admixture.

[0027] According to certain embodiments, acids (DA) comprising ionisable groups can be used [acids (IDA)] as polycondensation monomers of polyamide (A); among these ionisable groups, mention can be notably made of phenolic hydroxylic groups, sulfonic groups (generally aromatic sulfonic groups), phosphonic groups, onium goups (including phosphonium and ammonium groups) and the like. Non-limiting examples of acids (IDA) of this type which can be used within the frame of the present invention are notably 4- hydroxyisophthalic acid, 5-hydroxyisophthalic acid, 2-hydroxyterephthalic acid, 2,5-dihydroxyterephthalic acid, 4,6-dihydroxyisophthalic acid, 5- sulfoisophthalic acid (and salts thereof, e.g. Li, K, Na, Ag salts), and 2- sulfoterephthalic acid (and salts thereof, e.g. Li, K, Na, Ag salts).

[0028] Acids (IDA) including ionisable groups may be used in combination with aliphatic, cycloaliphatic, aromatic, arylaliphatic and alkylaromatic acids(DA), as above detailed.

[0029] In one embodiment, the method of present invention employs polyamide made from linear or branched aliphatic acids (DA) having from 3 to 8 carbon atoms wherein linear aliphatic acids (DA) are preferred.

[0030] In a preferred embodiment, the method of present invention employs

polyamide made from linear aliphatic acids (DA) having from 4 to 7 carbon atoms.

[0031] In a most preferred embodiment, the method of present invention employs polyamide made from adipic acid.

[0032] As disclosed above in the context of defining group X of formula (I), the polyamide must comprise at least one amine (NN) of the group consisting of bis(aminomethyl)furane (FDA) and bis(aminomethyl)tetrahydrofurane

(THFDA). FDA and THFDA are disclosed in WO-A-2013/007585.

[0033] Further amines (NN) that may be employed to manufacture the polyamide according to the invention include amines selected from the group consisting of aliphatic diamines, aromatic diamines and mixtures thereof.

[0034] Said aliphatic diamines are typically aliphatic diamines having 2 to18 carbon atoms.

[0035] Said aliphatic diamine is advantageously selected from the group consisting of 1 ,2-diaminoethane, 1 ,2-diaminopropane, propylene-1 ,3-diamine,

1.3- diaminobutane, 1 ,4-diaminobutane, 1 ,5-diaminopentane, 1 ,5-diamino-2- methylpentane, 1 ,4-diamino-1 , 1 -dimethylbutane, 1 ,4-diamino-1 -ethylbutane,

1.4- diamino-1 ,2-dimethylbutane, 1 ,4-diamino-1 ,3-dimethylbutane, 1 ,4- diamino-1 ,4-dimethylbutane, 1 ,4-diamino-2,3-dimethylbutane, 1 ,2-diamino-1- butylethane, 1 ,6-diaminohexane, 1 ,7-diaminoheptane, 1 ,8-diamino-octane,

1 ,6-diamino-2,5-dimethylhexane, 1 ,6-diamino-2,4-dimethylhexane, 1 ,6- diamino-3,3-dimethylhexane, 1 ,6-diamino-2,2-dimethylhexane, 1 ,9- diaminononane, 1 ,6-diamino-2,2,4-trimethylhexane, 1 ,6-diamino-2,4,4- trimethylhexane, 1 ,7-diamino-2,3-dimethylheptane, 1 ,7-diamino-2,4- dimethylheptane, 1 ,7-diamino-2,5-dimethylheptane, 1 ,7-diamino-2,2- dimethylheptane, 1 ,10-diaminodecane, 1 ,8-diamino-1 ,3-dimethyloctane, 1 ,8- diamino-1 ,4-dimethyloctane, 1.8-diamino-2,4-dimethyloctane, 1 ,8-diamino- 3,4-dimethyloctane, 1.8-diamino-4,5-dimethyloctane, 1.8-diamino-2,2- dimethyloctane, 1.8-diamino-3,3-dimethyloctane, 1 ,8-diamino-4,4- dimethyloctane, 1 ,6-diamino-2,4-diethylhexane, 1 ,9-diamino-5- methylnonane, 1 ,1 1 -diaminoundecane and 1 ,12-diaminododecane, 1 ,13- diaminotridecane, 2,5-bis(aminomethyl)tetrahydrofurane, N-methyl-bis- hexamethylene-triamine.

[0036] The aliphatic diamine preferably comprises at least one diamine selected from the group consisting of 1 ,4-diaminobutane, 1 ,5-diaminopentane, 1 ,5- diamino-2-methylpentane, 1 ,6-diaminohexane, 1 ,8-diamino-octane, 1 ,10- diaminodecane, and mixtures thereof. More preferably, the aliphatic alkylene diamine comprises at least one diamine selected from the group consisting of 1 ,4-diaminobutane, 1 ,5-diaminopentane, 1 ,6-diaminohexane and mixtures thereof. Even more preferably, the aliphatic alkylene diannine is 1 ,6- diaminohexane.

[0037] The aromatic diamine is preferably selected from the group consisting of meta-phenylene diamine, meta-xylylene diamine and para-xylylene diamine.

[0038] According to other embodiments, at least one of the amine (NN) is a

cycloaliphatic diamine, i.e. a diamine comprising a cycloaliphatic group

[amine (cNN)]; the amine (cNN) is generally selected from the group consisting of isophoronediamine, bis(3,5-dialkyl-4-aminocyclohexyl)methane, bis(3,5-dialkyl-4-aminocyclohexyl)ethane, bis(3,5-dialkyl-4-aminocyclohexyl) propane, bis(3,5- dialkyl-4-aminocyclohexyl) butane, bis(3-methyl-4- aminocyclohexyl)methane, p-bis(aminocyclohexyl)methane,

isopropylidenedi(cyclohexylamine), 4,4'-diamino-3,3'- dimethyldicyclohexylmethane, and 1 ,4-diaminocyclohexane.

[0039] According to certain other embodiments, at least one amine (NN) comprising ethereal bonds can be used [amine (NNE)] as polycondensation monomer of the polyamide; exemplary embodiments of amine (NNE), otherwise referred to as polyetherdiamines are notably diamines comprising moieties of formula: -(OCH₂-CHR^J)_n-, with R^J being H or a C1-C3 alkyl group, preferably -CH₃, and n being an integer of 1 to 15 and diamines comprising moieties of formula: - O-C(R'^J)(R"^J)-O-, with R'^J and R"^J, equal to or different from each other and at each occurrence, being H or a C1-C3 alkyl group, preferably -CH3.

[0040] Exemplary embodiments thereof are amines (NNE) of any of formulae 1 ) - 4):

1 )

with x, and z being zero or integers, with y being an integer, with the provisio that x+y+z is an integer of 1 to 15;

2)

with q being an integer of 1 to 15;

3)

with each of x, equal to or different from each other, being an integer of 1 to

6;

4)

wherein R^* and R'^*, equal to or different from each other, are independently hydrogen, a C1 -C3 alkyl group; A is alkyl, alkenyl, alkenene, alkylene-hetero- alkylene, alkylene-heterocyclo-alkylene, alkylene, alkylene-oxy-alkylene, 1 ,4- alkyl substituted piperazine, carbonyl, thiocarbonyl; B is alkyl, alkenyl, alkenene, alkylene-hetero-alkylene, alkylene-heterocyclo-alkylene, alkylene, alkylene-oxy-alkylene, 1 ,4-alkyl substituted piperazine, carbonyl,

thiocarbonyl; amines complying with this structural formula are notably disclosed in WO-A-2013/007128.

[0041] Generally, the molecular weight of the preferred amines (NNE) will be of at most 400, more preferably at least 200, even more preferably at most 150 g/mol. Amines (NNE), as detailed above, are notably available under trade name Jeffamine or Elastamine from Huntsmann Chemicals. Specific examples thereof include notably 2,2'-oxydiethanamine, 2,2'- (ethylenedioxy)bis(ethylamine), ethylene glycol bis(3-aminopropyl) ether.

[0042] It is within the scope of the invention to add to mixture (M1) at least one

polyfunctional acid/amine monomers comprising more that two carboxylic acid/amine groups, e.g. polycarboxylic acid having three or more carboxylic acid groups, polyamines having three or more amine groups. Incorporation of said polyfunctional acid/amine monomers generally lead to branched structures, star-like or tree-like, such as those described in WO-A- 97/24388 and WO-A-99/64496. [0043] It is also further understood that one or more than one end capping agent [agent (M)] can be added to mixture (M1 ) for the manufacture of polyamide, without this departing from the scope of the invention. The agent (M) is generally selected from the group consisting of an acid comprising only one reactive carboxylic acid group [acid (MA)] and an amine comprising only one reactive amine group [agent (MN)].

[0044] Acid (MA) is preferably selected from the group consisting of acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, lauric acid, stearic acid, cyclohexanecarboxylic acid, benzoic acid, 3-sulfobenzoic acid (and salts thereof, e.g. Li, K, Na, Ag salts), 4-sulfobenzoic acid (and salts thereof, e.g. Li, K, Na, Ag salts), preferably from acetic acid and benzoic acid.

[0045] Amine (MN) is preferably selected from the group consisting of methylamine, ethylamine, butylamine, hexylamine, octylamine, benzylamine, aniline, toluidine.

[0046] One of ordinary skills in the art will select through routine experimentation mixtures (M1 ), as detailed above, which are such to provide a polyamide that is not softening too much under the processing conditions and

possesses a water uptake or dissolution behaviour permitting its easy removal from the 3D shaped parts via easy techniques.

[0047] Preferred mixtures (M1 ) are selected from:

(a) mixtures comprising THFDA and adipic acid;

(b) mixtures comprising FDA and adipic acid;

(c) mixtures comprising THFDA and pimelic acid;

(d) mixtures comprising FDA and pimelic acid.

[0048] The polyamide involved in the present invention, that is to say the polyamide comprising from 60 mol.% to 100 mol.% of recurring units represented by formula (I)

- C(O)-A-C(O)-NH-X-NH- (I)

is advantageously semi-crystalline.

[0049] As herein used, the terms "semi-crystalline polyamide" are intended to

denote a polyamide which has a melting peak, as observed by differential scanning calorimetry (DSC). The DSC test can be made according to ASTM D3418.

[0050] Preferably, the polyamide involved in the present invention has a melting point (Tm) between 100 °C to 260 °C, as measured by differential scanning calorimetry (DSC) according to ASTM D3418.

[0051] According to certain embodiments, the support material of the invention

comprises at least one water-soluble polymeric additive different from the polyamide. The choice of the polymeric additive is not particularly critical, provided that it has sufficient thermal stability to be admixed with the polyamide, and it is soluble in water, that is to say, possessing a solubility of at least 1 % in water at a temperature of below 100 °C under atmospheric pressure. Polyelectrolytes such as polyacids (and their salts) and polyamines (and their salts), as well as non-ionizable polymers possessing water solubility can be advantageously used; this additive is generally selected from the group consisting of polyethyleneglycol (PEG) polymers;

polyvinylpyrrolidone (PVP) polymers; polymethylenenaphthalene sulfonates (obtained by sulfonation of naphthalene, condensation with formaldehyde and neutralization) polymers; styrene sulfonate polymers having -SOsXa groups, with X_a being H or a metal, e.g. Na, K, Li, including polystyrene sulfonates and copolymers of styrene-co-styrene sulfonate; sulfonated sulfone polymers having -SOsXa groups, with X_a being H or a metal, including sulfonated polysulfones, sulfonated polyphenylsulfones, sulfonated polyethersulfones; polysuccinimides and salts; polyaspartic acids and salts; poly(meth)acrylic acids and salts (e.g. Na, K, Li); polyvinyl sulfonic acids and salts (e.g. Na, K, Li); polyvinylalcohols and the like.

[0052] When present, the water soluble polymeric additive is added to the

polyamide in the support material in an amount of at least 1 % by weight, preferably at least 2 % by weight, more preferably at least 5 % by weight and/or generally of at most 30 % by weight, preferably at most 25 % by weight, more preferably at most 20 % by weight with respect to the total weight of support material.

[0053] The support material of the invention may also include other additives

different from the polyamide and the water soluble polymeric additives; these additives are selected from those generally known for polyamides, and include notably fillers, colorants, plasticizers, stabilizers, and combinations thereof.

[0054] In embodiments that include fillers, preferred concentrations of the fillers in the support material range from 1 % to 30 % by weight, with respect to the total weight of the support material. Suitable fillers include calcium carbonate, magnesium carbonate, glass fibers, graphite, carbon black, carbon fibers, talc, wollastonite, mica, alumina, silica, titanium dioxide, kaolin, silicon carbide, zirconium tungstate, and combinations thereof.

[0055] In certain embodiments, the support material of the present invention

consists of:

- more than 50 %, up to 100 % by weight of polyamide, as above detailed;

- from 0 to 30 % by weight of water soluble polymeric additive, as above detailed; and

- from 0 to 30 % by weight of other additives,

with respect to the total weight of the support material.

[0056] Preferably, the support material of the present invention consists of:

- from 75 to 100 % by weight of polyamide, as above detailed;

- from 0 to 20 % by weight of water soluble polymeric additive, as above detailed; and

- from 0 to 20 % by weight of other additives, as above detailed,

with respect to the total weight of the support material.

[0057] The support material is advantageously soluble or dispersible in water; it is preferably soluble in water. Dispersible in water, for the purposes of the present invention, shall mean that the support material, including the polyamide, exhibits a certain water uptake as specified below, swells or loses its shape in the presence of water but stays suspended in water, and not form a homogeneous solution. A support material, including the

polyamide, is referred to as soluble, when it will dissolve in water and become part of a homogeneous solution.

[0058] The water uptake of the support material at saturation, by immersion in water at 23 °C, is of at least 25 % by weight, preferably of at least 40 % by weight of the support material. This water uptake can be determined by providing a specimen shaped according to ISO527 in its dry state (moisture content of less than 0.2 % by weight), immersing the same in deionized water at 23 °C, until reaching a constant weight. The water uptake is calculated according to the formula:

Water uptake = ^{Wafler ~ Wbefore} x 100

b_efore

wherein Wbefore is the weight of the shaped specimen in its original dry state and Wafter is the weight of the shaped specimen after water uptake.

[0059] According to certain embodiments, the polyamide is a polyamide which at a temperature of below 100 °C under atmospheric pressure has a solubility in water of at least 25 % by weight, preferably 50 % by weight, and most preferably it is completely soluble in water.

[0060] Solubility of the polyamide of the present invention can be enhanced by

employing mixtures of water and aliphatic alcohols (including notably methanol, ethanol, isopropanol, ethylene glycol) at a temperature of below 100 °C, under atmospheric pressure.

[0061] Pursuant to preferred embodiments, the polyamide of the support structure has a wide processing window of at least 80 °C, preferably at least 100 °C, more preferably at least 130 °C. The term processing window for the puposes of the present invention is referred to as the difference ^^1 % minus T_m , i.e. between the temperature (T₍j_eg1 %) at which 1 % weight loss occurs (employing a heating rate of 10 °C/min) and the melting temperature T_m (as determined according to ASTM D3418). Polyamides having a wide processing window are particularly useful for fused filament fabrication (FFF) to be employed as support materials in 3D printing.

[0062] The support material of the present invention is used to print support

structures in additive manufacturing systems, such as extrusion-based additive manufacturing systems, and jetting-based additive manufacturing.

[0063] The support material is provided generally in a dry state; to this aim, the support material is generally dried prior to being delivered to and used in the additive manufacturing system.

[0064] As such, the support material provided to the additive manufacturing system preferably has a moisture content of less than 0.5 % by weight, preferably of less than 0.2 % by weight, with respect to the total weight of the support material. A preliminary drying step may be required to achieve this low moisture content by heating between 60 to 200 °C the support material at atmospheric temperature (under air or nitrogen) or under vacuum for the desired amount of time

[0065] The part material provided in the method of the present invention is generally a material requiring a processing temperature of at most 300 °C. The term processing temperature for the purposes of the present invention is referred to as the temperature of the nozzle of the printer. Part materials which are generally associated in the method of the invention to the support material, as above detailed, are selected from the group consisting of amorphous polymers having a glass transition temperature, as determined according to ASTM E1356, of from 100 to 180 °C, and semi-crystalline polymers having a melting point, as determined according to ASTM D3418, of from 100 °C to 260 °C.

[0066] The limitation of the part material's processing temperature serves to avoid softening of the support material under the part material's processing conditions. Deformation would render them ineffective as support structure materials.

[0067] More specifically, the part material is selected from the group comprising polymethyl methacrylate (PMMA), polycarbonate (PC), acrylonitrile butadiene styrene (ABS), polyamides, including notably polyamide 6, polyamide 1 1 , polyamide 610, polyamide 612, polyamide 510, polyamide 1010, polyamide 1012, polyamide 1212, polyamide MXD6, polyamide 66, polyamide 106, polyamide 12 and their copolyamides, polyester, including notably

polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene terephthalate (PET), polylactic acid (PLA), polyolefins, including notable polyethylene (PE) and polypropylene (PP), polyvinylidene fluoride (PVDF), polyetherimide (PEI) thermoplastic elastomers (TPE), thermoplastic polyurethane (TPU), and the like.

[0068] Generally, the step of printing layers of the three-dimensional object from the part material is hence carried out printing part material in the molten state at a temperature of at most 300°C. [0069] According to certain preferred embodiments, the method of the invention is a method for manufacturing a three-dimensional object with an extrusion-based additive manufacturing system, otherwise known also as fused filament fabrication technique.

[0070] The support material, according to these embodiments, is provided under the form of a filament. The filament may have a cylindrical or substantially cylindrical geometry, or may have a non-cylindrical geometry, such as a ribbon filament geometry; further, filament may have a hollow geometry, or may have a core-shell geometry, with the support material of the present invention being used to form either the core or the shell.

[0071] Yet, the support material, according to these embodiments may be also

provided in powder form, e.g. for being fed through an auger-pump print head.

[0072] When the method is an extrusion-based additive manufacturing system, the step of printing layers of a support structure from the provided support material comprises :

a) feeding the support material to a discharge head member having a throughbore ending with a discharge tip, and a circumferential heater to melt the material in the throughbore;

b) compressing the support material with a piston, for example with the unmelted filament acting as a piston, in said throughbore, while

simultaneously melting the support material in the discharge head member, so as to extrude a ribbon of support material from the discharge tip; and c) ensuring relative movement in x and y directions of the discharge tip and of a receiving platform while discharging support material on said receiving platform to form the cross sectional shape of the support structure; and d) ensuring relative movement in the z direction of the discharge tip and the receiving platform while discharging support material on said receiving platform to form the support structure in elevation.

[0073] According to these embodiments, the step of printing layers of the three- dimensional object from the provided part material in coordination with the printing of the layers of the support structure, advantageously further comprises: a') feeding the part material to a discharge head member having a

throughbore ending with a discharge tip, and a circumferential heater to melt the material in the throughbore;

b') compressing the part material with a piston, for example with the unmelted filament acting as a piston, in said throughbore, while

simultaneously melting the part material in the discharge head member, so as to extrude a ribbon of part material from the discharge tip; and

c) ensuring relative movement in x and y directions of the discharge tip and the receiving platform bearing the support structure, while discharging support material on said receiving platform and said support structure to form the cross sectional shape of the three-dimensional object, and

d) ensuring relative movement in the z direction of the discharge tip and the receiving platform while discharging part material on said receiving platform and said support structure, to form the three-dimensional object in elevation.

[0074] The method of the invention upon removing at least a portion of the support structure from the assembly so as to obtain the three-dimensional object may further involve exposing the assembly to water vapour and/or to water.

[0075] When exposing to water in the liquid state, pure water can be used.

Nevertheless, exposure to water solutions acidified or basified through the addition of acid(s) or base(s), to water mixtures with polar protic solvents (e.g. ethanol, isopropanol, ethylene glycol); to water solutions comprising electrolytes (e.g. sodium chloride, lithium chloride) can be used. Generally water is present in the liquid medium used for this exposure in a

concentration of at least 30 % wt, preferably at least 50% wt.

[0076] This exposure can be realized in any manner.

[0077] According to certain embodiments the step of removing at least a portion of the support structure from the assembly so as to obtain the three- dimensional object includes exposing the assembly to moist air, e.g. to air possessing a relative humidity (RH) of at least 70 %, preferably at least 80 %, preferably at least 85 %, at the temperature of exposure. This exposure to moist air can be effected at room temperature (i.e. at about 20 - 25 °C), but it is generally preferred to expose the assembly to moist air at a temperature of at least 50°C, preferably of at least 60°C and/or generally at a temperature of at most 90°C, preferably of at most 80°C.

[0078] According to other embodiments, the step of removing at least a portion of the support structure from the assembly so as to obtain the three- dimensional object includes contacting/immersing the assembly with/in water (i.e. liquid water). In this case, the water temperature for the

immersing/contacting is generally about room temperature, i.e. temperatures of from 20 to 25 °C, although higher temperatures may equally be used, up to about 100 °C.

[0079] The duration of exposure to water vapour and/or to water is not particularly limited, and exposure times of at least 1 hour may be effective.

[0080] It is nevertheless understood that when the step of removing at least a

portion of the support structure from the assembly so as to obtain the three- dimensional object comprises exposing the assembly to moist air, duration of exposure is preferably of at least 24 hours, preferably 30 hours.

[0081] As an outcome of the step of removing at least a portion of the support

structure from the assembly so as to obtain the three-dimensional object, the support structure is removed from the assembly; the said support structure can be advantageously detached from the three-dimensional object and removed in its solid form. Nevertheless, for embodiment's wherein use is made of a polyamide soluble in water, as above detailed, the removal of the support structure can be achieved through at least partial solubilization in water.

[0082] A further embodiment encompasses a composition of

(i) a polyamide comprising from 60 mole percent to 100 mole percent of recurring units represented by formula (I):

- C(O)-A-C(O)-NH-X-NH- (I), wherein

A represents a divalent hydrocarbon based group chosen from saturated or unsaturated aliphatics, saturated or unsaturated cycloaliphatics, aromatics comprising at least 5 carbon atoms, arylaliphatics and alkylaromatics; and X represents a divalent group of formula (II) or (III), and

(ii) a solvent.

[0083] In a preferred embodiment, the solvent comprises at least 75 % by weight, more preferably 85 % by weight, most preferably 95 % by weight of water.

[0084] In a further preferred embodiment, the composition comprises from 0.1 to 90 % by weight, preferably from 1 to 50 % by weight, more preferably from 5 to 25 % by weight of polyamide, based on the total weight of the composition.

[0085] A further embodiment encompasses a method to recover polyamide from the above disclosed composition comprising the steps of:

(i) leaving the composition to effect separation into an upper phase and a bottom phase,

(ii) decanting the upper phase comprising the majority of the water, and (iii) recovering polyamide from the bottom phase comprising the majority of the polyamide.

[0086] In a preferred embodiment, cooling is employed in step (i) to expedite phase separation.

[0087] In one embodiment, said composition of polyamide and solvent, preferably water, is for example obtained upon removing at least a portion of the support structure according to the invention from the assembly so as to obtain the three-dimensional object by exposing the assembly to liquid water. At exposure temperatures close to the boiling point of water, e.g. 80 °C, the poyamide of the support structure will completely dissolve in the water. Upon cooling or by simply letting sit the obtained solution, phase separation will occur into an an upper phase comprising the majority of the solvent and a bottom phase comprising the majority of the polyamide in the form of a dispersion. The polyamide rich phase can be won by simple decantation of the solvent rich phase. Polyamide can be recovered from the polyamide rich phase by appropriate drying processes and polyamide be reused in the additive manufacturing system.

[0088] Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall prevail.

[0089] Examples

[0090] Raw Materials

[0091] A1. adipic acid (Rhodiacid® AA) having a melting point of 152 °C from

Solvay.

[0092] A2. sebacic acid having a melting point of 134 °C from Merck.

[0093] A3. 2,5-bis(aminomethyl)tetrahydrofurane (THFDA) was synthesized as

disclosed in WO 2013/007585 A1 , the whole content of which is herein incorporated by reference.

[0094] Testing

[0095] Melting point (T_m), glass transition temperature (Tg) and crystallization

temperature (T_c) of polymers are determined by differential scanning calorimetry (DSC), using a Perkin Elmer Pyris 1 instrument, at a rate of 10

°C/min after removal of the thermal history of the sample at 250 °C.

[0096] Thermogravimetric analysis (TGA) is carried out on a Perkin-Elmer TGA4000 instrument on samples of around 10 mg, by heating at 10 °C/min under a flow of nitrogen up to 600 °C.

[0097] The number average molecular weight M_n (expressed in g/mol) is calculated by the equation M_n =2,000,000/(sum of end groups concentrations). The end groups, amine end groups (AEG) and carboxylic acid end groups (CEG), of the polyamides are determined by potentiometric titration and expressed in meq/kg. The number average molecular weight is then determined by the equation M_n = 2,000,000/(AEG+CEG), and expressed in g/mol.

[0098] Affinity with water: Before the test, the polyamides are dried for 2 hours at 160 °C under vacuum. After this thermal annealing process, the polyamides are fully crystallized. 0.5 g of polyamide is placed in a vial and deionized water is introduced to reach a concentration of polyamide of 250 g/L. The mixture is then placed at 25 °C or 80 °C for a given time under stirring. The observed behavior of the polymer is characterized as: soluble in water (S), dispersed in water (D), swollen by water (SW) or non-soluble in water (NS). Water absorption is calculated employing the formula (w(final)- w(initial))/w(initial). wherein Winitiai is the weight of the polyamide in its original dry state (after thermal annealing, before immersion) and Wfinai is the weight of the polyamide after immersion. Obtained results are collected in Table 1.

[0099] Synthesis of polyamide PA THF6

[00100] 56.15 g (0.384 mol) of adipic acid, 50.66 g (0.389 mol) of 2,5- bis(aminomethyl)tetrahydrofurane (THFDA), 0.13 g of sodium hypophosphite, 96 g of deionized water and 0.94 g of an antifoaming agent are placed in a a polymerization reactor. After introduction of the reactants, the reactor is purged 4 times with nitrogen, closed and agitation started. The pressure release valve is set at 18.5 bar. The reactor is heated under a pressure of 18.5 bar until the temperature of the reaction medium reaches 240 °C

(indiated by distillation of water). Subsequently, the reactor is decompressed down to a vacuum of 0.17 bar accompanied by heating of the reaction medium to 260 °C. The reaction mixture is then maintained at 0.17 bar, 260 °C for 20 min. At the end of the polymerization reaction, the polymer melt is extruded from the reactor (under nitrogen pressure).

[00101] Polyamide PA THF6 has a T_g of 68 °C, T_c of 158 °C and T_m of 202 °C. The thermal analyses by TGA indicates a very good thermal stability with only 1 % weight loss at 316 °C (T₍j_eg1 %=316 °C), which provides a large processing window in the melt (difference between ^^1 % and T_m of 1 14 °C, which is large compared to the narrow (30 °C) processing window of polyglycolic acid (PGA)) and hence provides a good opportunity to generate filaments from polyamide PA THF6 using a melt extrusion process. [00102] Synthesis of polyamide PA THF10 (Comparative Example)

[00103] The same process as for PA THF6 is used to produce PA THF10, employing an equimolar amount of sebacic acid instead of adipic acid. Polyamide PA THF10 has a T_g of 47 °C, T_c of 150 °C and T_m of 197 °C.

[00104] Table 1

Water solubility data

[00105] Comparative polyamide PA THF10 is not soluble or dispersed in water, and its shape does not change after prolonged exposure to water. Only 8.3 % by weight of water is absorbed at saturation, based on the initial weight of PA THF10, which is comparable to polyamide 66. PA THF10 cannot be used as a filament for water soluble/dispersible support material structures for 3D printing, despite of its good thermal properties.

[00106] Surprisingly, PA THF6 has a wide processing window allowing the generation of filaments to be used as a support material for amorphous polymers having a glass transition temperature of from 100 to 180 °C and semi-crystalline polymers having a melting point of from 100 °C to 260 °C. PA THF6 quickly disperses, and at elevated temperatures even dissolves in water which makes it suitable for 3D printing applications, especially as support material for fused filament fabrication (FFF).

[00107] A dispersion of PA THF6 in water will phase separate over time, with a layer of water separating at the top and a liquid bottom layer composed of PA THF6 and water.

Claims

Claim 1. A method for manufacturing a three-dimensional object with an additive manufacturing system, comprising:

- providing a support material comprising more than 50 wt.% of at least one polyamide wherein the polyamide comprises from 60 mol.% to 100 mol.% of recurring units represented by formula (I):

- C(O)-A-C(O)-NH-X-NH- (I) wherein

- providing a part material;

- printing layers of a support structure from the provided support material, and printing layers of the three-dimensional object from the provided part material in coordination with the printing of the layers of the support structure to provide an assembly of support structure and three-dimensional object, wherein at least a portion of the printed layers of the support structure support the printed layers of the three-dimensional object; and

- removing at least a portion of the support structure from the assembly so as to obtain the three-dimensional object.

Claim 2. The method of claim 1 , wherein A represents a linear or branched

alkylene group having from 1 to 6 carbon atoms.

Claim 3. The method of claim 1 or 2, wherein A represents a linear alkylene group having from 1 to 6 carbon atoms.

Claim 4. The method of any of claims 1 to 3, wherein the A represents a linear alkylene group having 4 carbon atoms and X represents the group of formula (III).

Claim 5. The method of any of the preceding claims, wherein the polyamide is a condensation product of at least one mixture comprising at least a diacid [acid

(DA)] (or derivative thereof) and at least a diamine [amine (NN)] (or derivatives thereof).

Claim 6. The method of any of the preceding claims, wherein the polyamide is a semi-crystalline polyamide having a melting point (Tm) between 100 °C to 260 ° C, as measured by differential scanning calorimetry (DSC) according to ASTM D3418.

Claim 7. The method of any of the preceding claims, wherein the support

material comprises at least one water-soluble polymeric additive different from the polyamide, which is generally selected from the group consisting of

polyethyleneglycol (PEG) polymers; polyvinylpyrrolidone (PVP) polymers;

polymethylenenaphthalene sulfonates (obtained by sulfonation of naphthalene, condensation with formaldehyde and neutralization) polymers; styrene sulfonate polymers having -SOsXa groups, with X_a being H or a metal, e.g. Na, K, Li, including polystyrene sulfonates and copolymers of styrene-co-styrene sulfonate; sulfonated sulfone polymers having -SOsXa groups, with X_a being H or a metal, including sulfonated polysulfones, sulfonated polyphenylsulfones, sulfonated polyethersulfones; polysuccinimides and salts; polyaspartic acids and salts;

poly(meth)acrylic acids and salts (e.g. Na, K, Li); polyvinyl sulfonic acids and salts (e.g. Na, K, Li); and polyvinylalcohols.

Claim 8. The method of any of the preceding claims, wherein the support

material is provided in a dry state, having a moisture content of less than 0.5 wt.%, preferably of less than 0.2 wt.%, based on the total weight of the support material.

Claim 9. The method of any of the preceding claims, wherein the step of printing layers of the three-dimensional object from the part material is carried out by printing part material at a temperature of at most 300 °C.

Claim 10. The method of any of the preceding claims, wherein the part material is selected from the group consisting of polymers having a glass transition temperature (Tg) between 100°C and 180°C and no melting peak, as measured by differential scanning calorimetry (DSC) according to ASTM E1356 and semi- crystalline polymers having a melting point (Tm) between 100 °C to 260 °C, as measured by differential scanning calorimetry (DSC) according to ASTM D3418.

Claim 1 1. The method of any of the preceding claims, wherein the part material is selected from the group comprising polymethyl methacrylate (PMMA),

polycarbonate (PC), acrylonitrile butadiene styrene (ABS), polyamides, including notably polyamide 6, polyamide 1 1 , polyamide 610, polyamide 612, polyamide 510, polyamide 1010, polyamide 1012, polyamide 1212, polyamide MXD6, polyamide 66, polyamide 106, polyamide 12 and their copolyamides, polyester, including notably polybutylene terephthalate (PBT), polytrimethylene

terephthalate (PTT), polyethylene terephthalate (PET), polylactic acid (PLA), polyolefins, including notable polyethylene (PE) and polypropylene (PP), polyvinylidene fluoride (PVDF), polyetherimide (PEI) thermoplastic elastomers (TPE) and thermoplastic polyurethane (TPU).

Claim 12. The method of any of the preceding claims, wherein the additive

manufacturing system is an extrusion-based additive manufacturing system, otherwise known also as fused filament fabrication technique.

Claim 13. The method of any of claims 9 to 12, wherein the step of printing layers of a sacrificial support structure from the provided support material comprises : a) feeding the support material to a discharge head member having a

b) compressing the support material with a piston, for example with the unmelted filament acting as a piston, in said throughbore, while simultaneously melting the support material in the discharge head member, so as to extrude a ribbon of support material from the discharge tip; and

c) ensuring relative movement in x and y directions of the discharge tip and of a receiving platform while discharging support material on said receiving platform to form the cross sectional shape of the sacrificial support structure; and

d) ensuring relative movement in the z direction of the discharge tip and the receiving platfornn while discharging support material on said receiving platform to form the sacrificial support structure in elevation.

Claim 14. The method of claim 13, wherein the step of printing layers of the three- dimensional object from the provided part material in coordination with the printing of the layers of the sacrificial support structure, advantageously further comprises:

a') feeding the part material to a discharge head member having a throughbore ending with a discharge tip, and a circumferential heater to melt the material in the throughbore;

b') compressing the part material with a piston, for example with the unmelted filament acting as a piston, in said throughbore, while simultaneously melting the part material in the discharge head member, so as to extrude a ribbon of part material from the discharge tip; and

c) ensuring relative movement in x and y directions of the discharge tip and the receiving platform bearing the sacrificial support structure, while discharging support material on said receiving platform and said sacrificial support structure to form the cross sectional shape of the three-dimensional object, and

d) ensuring relative movement in the z direction of the discharge tip and the receiving platform while discharging part material on said receiving platform and said sacrificial support structure, to form the three-dimensional object in elevation.

Claim 15. The method of any of the preceding claims, wherein the step of

removing at least a portion of the support structure from the assembly so as to obtain the three-dimensional object involves exposing the assembly to water vapour and/or to water.

Claim 16. The method of claim 15, wherein the step of removing at least a portion of the support structure from the assembly so as to obtain the three-dimensional object comprises exposing the assembly to air possessing a relative humidity (RH) of at least 70 %, preferably at least 80 %, more preferably at least 85 %, at the temperature of exposure or wherein such step includes contacting/immersing the assembly with/in liquid water.

Claim 17. The method of any of the preceding claims, wherein the support

structure is removed from the assembly in its solid form or by at least partial solubilization.

Claim 18. A composition comprising:

- at least one polyamide comprising from 60 mol.% to 100 mol.% of recurring units represented by formula (I):

- C(O)-A-C(O)-NH-X-NH- (I) wherein

and at least one solvent.

Claim 19. The composition of claim 18, comprising from 0.1 to 90 wt. % of the polyamide, based on the total weight of the composition.

Claim 20. The composition of claim 19, comprising from 1 to 50 wt. % of the

polyamide.

Claim 21. The composition of claim 20, comprising from 5 to 25 wt.% of the

polyamide.

Claim 22. The composition of any one of claims 18 to 21 , whrein the solvent is water.

Claim 23. A method to recover polyamide from the composition as claimed in any of claims 18 to 22 comprising the steps of (i) leaving the composition to effect separation into an upper phase and a bottom phase, (ii) decanting the upper phase comprising the majority of the water, and (iii) recovering polyamide from the bottom phase comprising the majority of the polyamide.

Claim 24. Method of claim 23 wherein step (i) further comprises cooling the

composition to expedite phase separation.