POLYESTER POWDERS AND THE USE THEREOF IN THREE-DIMENSIONAL PRINTING PROCESSES

1 . A method of forming an object via an additive manufacturing process comprising the steps of:

a. providing a layer of a particulate composition, the particulate composition comprising a polyester powder having a melting point onset temperature (T m , onset), a crystallization onset temperature (T c , onset), and a sinterability region (T m , onset−T c , onset), wherein the sinterability region of the polyester powder is greater than 14° C., when determined in accordance with ISO 11357-1 (2009);

b. optionally, selectively depositing a liquid composition onto the layer of the particulate composition, wherein at least one of the particulate composition or liquid composition comprises a fusing agent;

c. applying electromagnetic radiation to at least one of:

(i) a specified location on the layer of the particulate composition, or

(ii) a location at which the liquid composition which has been selectively deposited onto the particulate composition;

wherein the particulate composition undergoes melting in at least some of the locations where the electromagnetic radiation and/or the liquid composition has been applied to form a fused section in accordance with computer data corresponding to a portion of a three-dimensional object to be formed; and

d. repeating steps (a), optionally (b), and (c) a plurality of times to form a fused three-dimensional object.

2 . The method of claim 1 , wherein the polyester powder comprises polybutylene terephthalate (PBT) or a copolymer thereof.

3 . The method according to claim 2 , wherein the polyester powder possesses a number average molecular weight from 20,000 g/mol to 50,000 g/mol, as determined by H-NMR, and wherein the sinterability region of the polyester powder is between 14-40° C.

4 . The method according to claim 2 , wherein the particulate composition further comprises one or more additives, wherein the additives comprise flame retardants, flow aids, fillers, pigments, or stabilizers.

5 . The method according to claim 2 , wherein the polyester powder is a polymer compound powder, wherein one or more flame retardants or glass beads are compounded into the polyester powder.

6 . The method according to claim 2 , wherein polyester powder possesses a D50 particle size of 30 to 80 μm wherein D50 is determined in accordance with ISO 13320-1.

7 . The method according to claim 2 , wherein the polyester powder is formed by a process comprising the steps of:

providing an oligoester having a number average molecular mass from 1000 g/mol to 5000 g/mol;

optionally, micronizing the oligoester to form an oligoester powder;

optionally, emulsion solidifying the oligoester or oligoester powder to form an emulsion-solidified oligoester powder; and

subjecting the oligoester powder or emulsion-solidified oligoester powder to a solid-state post condensation (SSPC) process;

wherein either the micronizing or emulsion solidifying steps, or both, are performed.

8 . The method according to claim 7 , wherein the oligoester is formed by combining a terephthalic acid (TPA)-based compound and a hydroxyl-containing compound at a temperature of between 140 to 230° C. in the presence of a catalyst.

9 . The method according to claim 7 , wherein the micronizing step comprises milling, wherein the milling further comprises a cryogenic milling, jet milling, or mechanical grinding process.

10 . The method according to claim 9 , wherein the milling step comprises a jet milling or mechanical grinding process, wherein the jet milling or mechanical grinding process is carried out at a temperature of 15 to 35° C.

11 . The method according to claim 7 , wherein the emulsion solidifying step involves the emulsification of the oligoester or oligoester powder in a silicone oil or ionic liquid solvent.

12 . The method according to claim 7 , wherein the SSPC step further comprises one or more of the following:

(i) heating the oligoester powder or emulsion-solidified oligoester powder at a temperature of greater than 165° C. for at least 5 hours;

(ii) optionally, applying a vacuum at a pressure from 0.01 millibar (mbar) to 10 mbar during the heating; and

(iii) optionally, applying an inert gas during the heating;

wherein the heating step involves heating the oligoester powder or emulsion-solidified powder to a temperature up to either

A. at most 10° C. less than the melting point of the oligoester powder or emulsion-solidified oligoester powder, or

B. less than the T m , onset of the oligoester powder or emulsion-solidified oligoester powder;

wherein melting point and T m , onset are determined in accordance with ISO 11357-3 (2009).

13 . The method according to claim 8 , wherein TPA-based compound consists essentially of TPA or dimethyl terephthalate, and wherein the hydroxyl-containing compound consists essentially of 1,4-butanediol, and wherein the oligoester consists essentially of oligo-butylene terephthalate (OBT).

14 . The method according to claim 2 , wherein the polyester powder consists essentially of PBT or a copolymer thereof, and wherein the PBT or copolymer thereof possesses a sinterability region of between 15-40° C.

15 . The method according to claim 14 , wherein the polyester powder comprises a copolymer having a PBT hard block; and

wherein the polyester powder possesses a sinterability region of between 20-35° C.

16 . The method according to claim 15 , wherein the polyester powder consists of a copolymer having a block which is the reaction product of a dimer fatty acid, butanediol, dimethyl terephthalate, or polytetrahydrofuran.

17 . The method according to claim 16 , wherein the T m , onset of the copolymer is at least 120° C.

18 . The method according to claim 16 , wherein the T m , onset of the polyester powder is from 220° C. to 250° C.

19 . The method according to claim 2 , wherein step (b) is carried out, further wherein the fusing agent facilitates melting of the particulate composition and further comprises an energy absorber, a thermal initiator, or a photoinitiator.

20 . The method according to claim 2 , wherein the polyester powder comprises recycled powder.