Polymer composition for selective sintering
A polymer composition for the production of shaped objects via selective sintering includes ≥70.0 wt % of poly(ethylene terephthalate), wherein ≥25.0 wt % and ≤90.0 wt % of the poly(ethylene terephthalate has resulted from a selective sintering process as unsintered material. The polymer composition is a powder having a D 10 of ≥10 and ≤40 μm, a D 50 of ≥75 and ≤100 μm, and a D 90 of ≥160 and ≤200 μm. The polymer composition allows for the production of an article having a continuous use temperature of ≥100° C., and results in a low change of molecular weight during exposure to selective sintering powder processing temperatures. Further, the polymer composition allows for a significant reduction of the waste material generated during selective sintering as the unsintered material does not have to be disposed of as waste but may be used again.
1. A polymer composition for the production of shaped objects via selective sintering wherein the polymer composition comprises ≥70.0 wt % of a thermoplastic polyester, wherein ≥25.0 wt % and ≤90.0 wt % of the thermoplastic polyester has been subjected to a thermal treatment, and the thermoplastic polyester that has been subjected to a thermal treatment is a thermoplastic polyester that has resulted from a selective sintering process as unsintered material,
wherein the thermoplastic polyester is poly(ethylene terephthalate) having an intrinsic viscosity of ≥0.80 dl/g and ≤2.5 dl/g determined in accordance with ASTM D2857-95 (2007), a degree of crystallinity of ≥15.0%, and a heat of fusion of ≥50 J/g, and wherein the polymer composition is a powder having a D 10 of ≥10 and ≤40 μm, a D 50 of ≥75 and ≤100 μm, and a D 90 of ≥160 and ≤200 μm.
2. The polymer composition according to claim 1 , wherein the thermal treatment involves exposing the poly(ethylene terephthalate) to a temperature of more than 100° C. above the glass transition temperature T g and less than 10° C. below the peak melting temperature T p,m , wherein T g is determined in accordance with ISO 11357-2 (2013) and T p,m is determined in accordance with ISO 11357-3 (2011), first heating run.
3. The polymer composition according to claim 1 , wherein the thermal treatment is performed for ≥1 hour.
4. The polymer composition according to claim 1 wherein the thermal treatment involves exposing the poly(ethylene terephthalate) to a temperature of ≥170° C. and ≤230° C.
5. The polymer composition according to claim 1 , wherein ≥75.0 wt % of the poly(ethylene terephthalate) has been subjected to the thermal treatment.
6. The polymer composition according to claim 1 , wherein the poly(ethylene terephthalate) is a poly(ethylene terephthalate) homopolymer.
7. The polymer composition according to claim 1 , wherein the poly(ethylene terephthalate) has an intrinsic viscosity of ≥1.00 dl/g and ≤1.50 dl/g determined in accordance with ASTM D2857-95 (2007).
8. The polymer composition according to claim 1 , wherein the polymer composition comprises ≥90.0 wt % of the poly(ethylene terephthalate) with regard to the total weight of the polymer composition.
9. The polymer composition according to claim 1 , wherein the polymer composition further comprises ≥0.01 wt % and ≤5.00 wt % with regard to the total weight of the polymer composition of a flow agent selected from silica, alumina, phosphate, borate, titania, talc, mica, kaolin, attapulgite, calcium silicate, magnesium silicate or a combination thereof.
10. A process for the production of shaped objects using a polymer composition of claim 1 ,
wherein the process comprises the steps of:
(a) providing a quantity of a powder comprising the polymer composition of claim 1 ;
(b) irradiating a portion of the polymer composition with a radiation source, such that the particles in that portion of the polymer composition absorb sufficient heat to reach a temperature above the peak melting temperature T p,m determined via differential scanning calorimetry, first heating run in accordance with ISO 11357-1 (2009);
(c) terminating the exposure of the portion of the polymer composition to the irradiation source so that the temperature of the particles of the polymer composition decreases to below T p,m ; and
(d) removing the portion of the polymer composition that has not been subjected to irradiation by the energy source;
wherein steps (a) through (d) are executed in this sequence.
11. A shaped object produced from the composition of claim 1 by selective sintering process, wherein the shaped object has a porosity of ≤5.0%.
12. The polymer composition of claim 1 , wherein ≥50.0 wt % and ≤90.0 wt % of the poly(ethylene terephthalate) has been subjected to a thermal treatment.
13. The polymer composition of claim 1 , wherein ≥50.0 wt % and ≤80.0 wt % of the poly(ethylene terephthalate) has been subjected to a thermal treatment.