Polymer composition for selective sintering methods

Abstract

A polymer composition can be used in selective absorbing sintering, SAS, or selective inhibition sintering, SIS, methods. The polymer of the polymer composition has open mesopores, where a cumulative pore volume distribution of the mesopores, measured according to DIN 66134, is at least 0.01 cm.sup.3/g.

Claims

1. A polymer composition for selective absorbing sintering, or selective inhibition sintering, comprising: a polymer comprising open mesopores, which is obtained by a precipitation process, and a sintering absorber or a sintering inhibitor, wherein a cumulative pore volume distribution of the mesopores, measured according to DIN 66134, is 0.01 to 0.127 cm.sup.3/g, and wherein said polymer is a polyamide and said absorber or said inhibitor is within open mesopores of said polymer.

2. The polymer composition according to claim 1, wherein the cumulative pore volume distribution is at least 0.025 cm.sup.3/g.

3. The polymer composition according to claim 1, wherein the cumulative pore volume distribution is at least 0.035 cm.sup.3/g.

4. The polymer composition according to claim 1, wherein at least 30% of a sum total of open macro- and mesopores of the polymer composition having a pore diameter of 2 to 300 nm, measured according to DIN 66134, are open mesopores.

5. The polymer composition according to claim 1, wherein at least 50% of a sum total of open macro- and mesopores of the polymer composition having a pore diameter of 2 to 300 nm, measured according to DIN 66134, are open mesopores.

6. The polymer composition according to claim 1, wherein a BET surface area of the polymer composition, measured to DIN ISO 9277, is at least 7 m.sup.2/g to 30 m.sup.2/g.

7. The polymer composition according to claim 1, wherein a BET surface area of the polymer composition, measured to DIN ISO 9277, is from 10 m.sup.2/g to 30 m.sup.2/g.

8. The polymer composition according to claim 1, wherein a weight average particle diameter d.sub.50 of the polymer composition, measured by laser diffraction, is not more than 100 μm.

9. The polymer composition according to claim 1, wherein a weight average particle diameter d.sub.50 of the polymer composition, measured by laser diffraction, is from 10 μm to 80 μm.

10. The polymer composition according to claim 1, wherein a surface energy of a polymer in the polymer composition is 25 to 35 mN/m, the surface energy determined by a contact angle measurement by a capillary rise height method using a Washburn equation and an evaluation method according to Owens, Wendt, Rabel and Kaelble.

11. The polymer composition according to claim 1, wherein a surface energy of a polymer in the polymer composition is from 25 mN/m to 32 mN/m, the surface energy determined by a contact angle measurement by a capillary rise height method using a Washburn equation and an evaluation method according to Owens, Wendt, Rabel and Kaelble.

12. The polymer composition according to claim 1, which absorbs a liquid in a volume of 1,000 pl/g to 30,000 pl/g.

13. A shaped body, which comprises the polymer composition according to claim 1.

14. A shaped body, obtained by sintering the polymer composition according to claim 1.

15. A process for producing a polymer composition according to claim 1, the process comprising: a) at least partly dissolving a polymer in a solvent at a temperature of 10 K to 60 K above a dissolution temperature of the polymer, and then b) reducing the temperature down to a precipitation temperature to obtain the composition in the form of a suspension.

16. The process according to claim 15, further comprising: keeping the suspension, after precipitation, at a temperature of 2-10 K above the precipitation temperature for 10 min to 180 min.

17. The process according to claim 15, wherein said a) at least partly dissolving is effected at a dissolution temperature of 40 K to 60 K and the precipitation of said b) reducing is conducted at a temperature 3 K above the precipitation temperature or higher.

18. A process for producing a shaped body, the process comprising: performing selective absorbing sintering or selective inhibition sintering with a polymer composition according to claim 1 to shape the polymer composition into the shaped body.

Description

EXAMPLES

Example 1: Reprecipitation of Nylon-12 (PA 12)

(1) 400 kg of balanced PA 12 prepared by hydrolytic polymerization and having a relative solution viscosity of 1.57 and an end group content of 118 mmol/kg COOH or 9 mmol/kg NH2 were brought to 156° C. together with 1500 l of ethanol, denatured with 2-butanone and with water content 1%, in a 3000 l stirred tank, equipped with a paddle mixer, within 2.5 hours and left at this temperature while stirring at 75 rpm for 1 hour. Subsequently, the jacket temperature is reduced to 124° C. and, while continuously distilling the ethanol off at a cooling rate of 25 K/h at the same stirrer speed, the internal temperature is brought to 125° C. From then on, the jacket temperature was kept 2 K-3 K below the internal temperature at the same cooling rate. Thereafter, distillative removal was continued at a cooling rate of 40 K/h and hence the internal temperature was brought to 109° C. At this temperature, precipitation set in, noticeable from the evolution of heat. The distillation rate was increased until the internal temperature did not rise above 110° C. After 5 minutes, the internal temperature declined, which indicated the end of precipitation. Then the jacket temperature was raised again, by a maximum of 3° C., over a period of 80 min, before the temperature of the suspension was brought to 45° C. by further distillative removal and cooling via the shell and the suspension was then transferred into a paddle dryer. The ethanol was distilled off at 70° C./400 mbar and then the residue was subjected to further drying at 20 mbar/86° C. for three hours. This gave a precipitated PA 12 having a mean particle diameter of 91 μm. The bulk density was 435 g/l.

Example 2: Reprecipitation of Nylon-11 (PA 11)

(2) The polyamide was prepared according to example 7 of the U.S. Pat. No. 8,865,053 with a different internal temperature of 106° C. This gave a precipitated PA 11 having a mean particle diameter of 50 μm. The bulk density was 450 g/l.

Example 3: Reprecipitation of Nylon-12 (PA 12)

(3) 60 kg of balanced PA 12 prepared by hydrolytic polymerization and having a relative solution viscosity of 1.57 and an end group content of 118 mmol/kg COOH or 8 mmol/kg NH2 were brought to 145° C. together with 250 l of ethanol, denatured with 2-butanone and with water content 1%, in an 800 l stirred tank at 110 rpm within 2.5 hours and left at this temperature while stirring for 1 hour. Subsequently, the jacket temperature is reduced to 124° C. and, while continuously distilling the ethanol off at a cooling rate of 25 K/h at the same stirrer speed, the internal temperature is brought to 125° C. From then on, the jacket temperature was kept 2 K-3 K below the internal temperature at the same cooling rate. The internal temperature was brought to 117° C. at the same cooling rate and then kept constant for 60 minutes. Thereafter, distillative removal was continued at a cooling rate of 40 K/h and hence the internal temperature was brought to 111° C. At this temperature, precipitation set in, noticeable from the evolution of heat. The distillation rate was increased until the internal temperature did not rise above 111.3° C. After 25 minutes, the internal temperature declined, which indicated the end of precipitation. Then the jacket temperature was raised again, by a maximum of 2° C., over a period of 35 min, before the temperature of the suspension was brought to 45° C. by further distillative removal and cooling via the shell and the suspension was then transferred into a paddle dryer. The ethanol was distilled off at 70° C./400 mbar and then the residue was subjected to further drying at 20 mbar/86° C. for three hours.

(4) This gave a precipitated PA 12 having a mean particle diameter of 62 μm. The bulk density was 394 g/l.

Example 4: Reprecipitation of Nylon-12 (PA 12)

(5) 60 kg of partly balanced PA 12 prepared by hydrolytic polymerization in the presence of 0.4% dodecanedioic acid and having a relative solution viscosity of 1.57 and an end group content of 80 mmol/kg COOH or 40 mmol/kg NH2 were brought to 147° C. together with 250 l of ethanol, denatured with 2-butanone and with water content 1%, in an 800 l stirred tank within 2.5 hours and left at this temperature while stirring for 1 hour.

(6) Subsequently, the jacket temperature is reduced to 124° C. and, while continuously distilling the ethanol off at a cooling rate of 25 K/h at the stirrer speed of 108 rpm, the internal temperature is brought to 125° C. From then on, the jacket temperature was kept 2 K-3 K below the internal temperature at the same cooling rate. Thereafter, distillative removal was continued at a cooling rate of 40 K/h and hence the internal temperature was brought to 109° C. At this temperature, precipitation set in, noticeable from the evolution of heat. The distillation rate was increased until the internal temperature did not rise above 110° C. After 5 minutes, the jacket temperature was raised again, by a maximum of 4° C., over a period of 140 min, before the temperature of the suspension was brought to 45° C. by further distillative removal and cooling via the shell and the suspension was then transferred into a paddle dryer. The ethanol was distilled off at 70° C./400 mbar and then the residue was subjected to further drying at 20 mbar/86° C. for three hours.

(7) This gave a precipitated PA 12 having a mean particle diameter of 63 μm. The bulk density was 311 g/l.

Example 5: Nylon-12/10,12 (PA 12/1012)

(8) The polyamide was prepared according to example 7 of the U.S. Pat. No. 8,591,797. The pellets obtained were ground at low temperature by means of a pinned disc mill. This gave a ground nylon-12/10,12.

Example 6: Reprecipitation of Nylon-12 (PA 12) in the Presence of Glass Beads

(9) In accordance with Example 4, 60 kg of the following partly balanced PA12, rel. solution viscosity 1.78, COOH end groups 65 mmol/kg, NH2 end groups 29 mmol/kg, are reprecipitated under the following altered conditions in 250 l of EtOH in the presence of 40% by mass of glass beads (Swarcoforce C40-80):

(10) Stirrer speed 110 rpm. Dissolution temperature: 149° C., 2 hours. Precipitation temperature: nucleation phase prior to the actual precipitation at 115° C./30 min, followed by main precipitation phase at 109° C. The drying is effected as in Example 4.

Example 7: Reprecipitation of Partly Balanced PA12

(11) In accordance with Example 4, 60 kg of the following partly balanced PA12, rel. solution viscosity 1.68, COOH end groups 75 mmol/kg, NH2 end groups 49 mmol/kg, are reprecipitated under the following altered conditions in 250 l EtOH:

(12) Dissolution temperature: 175° C.

(13) Precipitation temperature: 114° C.

(14) The drying is effected as in Example 4.

Example 8: Reprecipitation of Partly Balanced PA12

(15) Example 7 repeated with the same starting polyamide under the following conditions:

(16) Dissolution temperature: 175° C.

(17) Precipitation temperature: 115° C.

(18) The drying is effected as in Example 4.

Example 9: Reprecipitating PA613

(19) According to Example 4, 40 kg of a PA 613 pellet specimen (rel. solution viscosity 1.81) are reprecipitated under the following precipitation conditions:

(20) Dissolution temperature: 175° C.

(21) Precipitation temperature: 128° C.

Example 10: Coprecipitation of PA12 and PA1013

(22) According to Example 4, 60 kg of a pellet mixture of unbalanced PA12 (rel. solution viscosity 1.62) and PA1013 (rel. solution viscosity 1.64) in a mass ratio of 85:15 are reprecipitated under the following modified precipitation conditions:

(23) Dissolution temperature: 175° C.

(24) Precipitation temperature: 112° C.

Example 11: Reprecipitation PA106

(25) According to Example 4, 60 kg of a PA 106 pellet specimen (rel. solution viscosity 1.84) are reprecipitated under the following modified precipitation conditions:

(26) Dissolution temperature: 175° C.

(27) Precipitation temperature: 142° C.

Example 12: Reprecipitating PA106

(28) According to Example 4, 60 kg of a PA 106 pellet specimen (rel. solution viscosity 1.62) are reprecipitated under the following modified precipitation conditions:

(29) Dissolution temperature: 175° C.

(30) Precipitation temperature: 142° C.

Example 13: Reprecipitation of PA66

(31) According to Example 4, 40 kg of a PA 66 pellet specimen (rel. solution viscosity 1.61) are reprecipitated under the following modified precipitation conditions:

(32) Dissolution temperature: 175° C.

(33) Precipitation temperature: 157° C.

Example 14: Reprecipitating PA12

(34) Example 3 is repeated with a dissolution temperature of 171° C. and a precipitation temperature of 114° C.

(35) The pore volume was ascertained according to DIN 66134 in a double determination.

(36) TABLE-US-00001 TABLE 1 cumulated pore volume of the polyamide compositions Mode of Cumulated pore Example Polyamide preparation d.sub.50 volume in cm.sup.3/g 1 PA12 precipitation 91 μm 0.015  2* PA11 precipitation 50 μm 0.002 3 PA12 precipitation 62 μm 0.037 4 PA12 precipitation 63 μm 0.072  5* PA12/1012 grinding not 0.0006 determined 6 PA12 precipitation 56 0.052 7 PA12 precipitation 63 0.12 8 PA12 precipitation 63 0.091 9 PA613 precipitation 59 0.088 10  PA12/1013 precipitation 46 0.101 11  PA106 precipitation 54 0.053 12  PA106 precipitation 40 0.111 13  PA66 precipitation 50-80 0.127 14  PA12 precipitation 58 0.053 *non-inventive