Method for producing a powder comprising at least one polymer and such a type of powder

Patent metadata

Field	Value
Publication number	US-12365115-B2
Application number	US-201917049511-A
Country	US
Kind code	B2
Filing date	Apr 23, 2019
Priority date	Apr 23, 2018
Publication date	Jul 22, 2025
Grant date	Jul 22, 2025

Abstract

A method for producing a powder comprising at least one polymer for use in a method for the additive manufacture of a three-dimensional object is described. The method includes the step of mechanically treating the powder in a mixer with at least one rotating mixing blade, wherein the powder is exposed to a temperature T B and T B is at least 30° C. and is below the melting point T m of the polymer (determined according to DIN EN ISO 11357) if the polymer is a semi-crystalline polymer, or wherein T B is at least 30° C. and wherein T B is at most 50° C. above the glass transition temperature T g of the polymer (determined according to DIN EN ISO 11357) if the polymer is a melt-amorphous polymer. Compared to a time before the start of the treatment, it may be achieved that after the treatment, the bulk density of the powder is increased by at least 10% (or in the case of polymer, copolymer or polymer blend of polyamide at least 2% and more) and the BET surface area is decreased by at least 10%, and optionally also the pourability is improved by at least 10%.

First claim

The invention claimed is:

1. A method for producing a powder comprising at least one polymer for use in a method for the additive manufacture of a three-dimensional object, comprising:
mechanically treating the powder in a mixer with at least one rotating mixing blade;
conducting at least one heat treatment, wherein the at least one heat treatment includes a T B heat treatment on the powder that heats the powder to a temperature T B and wherein the T B heat treatment is the only heat treatment that heats the powder to a temperature T B ;
wherein T B is at least 30° C. and wherein T B is below a melting point T m of the polymer (determined according to DIN EN ISO 11357) if the polymer is a semi-crystalline polymer; or
wherein T B is at least 30° C. and wherein T B is at most 50° C. above a glass transition temperature T g of the polymer (determined according to DIN EN ISO 11357) if the polymer is a melt-amorphous polymer; and
wherein the T B heat treatment consists of:
a heating phase defined by raising a heating temperature, starting from an initial temperature below T B , which exists when starting mechanically treating the powder, until the heating temperature reaches the temperature T B ; and
a holding phase defined by maintaining the heating temperature in a range of T B ±10° C. for a holding time; and

cooling the powder to a temperature of at most 35° C. after the T B heat treatment and before the powder is used in an additive manufacturing method,
wherein T B is defined by one or more of the following conditions or methods (i) to (vii):
(i) T B is above a heat deflection temperature HDT-A of the polymer (determined according to DIN EN ISO 75, measured in a reference measurement on a test specimen consisting only of the polymer, i.e. without any additives);
(ii) T B is above the heat deflection temperature HDT-A of the polymer (determined according to DIN EN ISO 75, measured in a reference measurement on a test specimen consisting only of the polymer, i.e. without any additives), wherein the polymer is a semi-crystalline polymer;
(iii) T B is at most 100° C. below the glass transition temperature T g of the polymer (determined according to DIN EN ISO 11357);
(iv) T B is at most 100° C. below the glass transition temperature T g of the polymer (determined according to DIN EN ISO 11357), wherein the polymer is a semi-crystalline polymer;
(v) T B is at most 100° C. below the glass transition temperature T g of the polymer (determined according to DIN EN ISO 11357), wherein the polymer is a melt-amorphous polymer;
(vi) for a polymer powder to be used, T B is at most a temperature T max determined in a temperature-current consumption measurement of the same polymer in a mixer with a mixing blade rotation in the range of 20 to 50 m/s during the heating process, wherein T max is determined in the temperature-current consumption measurement by one or both methods (a) or (b) as follows:
(a) maximum T B is determined by a temperature-current consumption diagram, wherein one data point is recorded every minute, wherein [(gradient/min)/current consumption] considered only in the range T g −20° C. to T m is at least greater than 5% and at most 30%; or
(b) maximum T B is determined by a temperature-current consumption diagram, wherein the current consumption of the mixer rises disproportionately strongly within a short time to an increased current consumption value I x , which fulfils at least one condition selected from the group consisting of the conditions:
I x is at least 10% higher than the average value of at least 10 preceding measuring points, recorded at at least one measurement per minute, wherein only current increases in the range T g −20° C. to T m are considered,
I x is at most 100% higher than the average value of at least 10 preceding measuring points, recorded at at least one measurement per minute, wherein only current increases in the range T g −20° C. to T m are considered;

(vii) T B is at the temperature T max ±10° C. or below the temperature T max at which a bulk density of the powder drops to a value below a bulk density of untreated powder as a result of use of the mixer, wherein the maximum T max is determined by a test series with different T B and otherwise the same mixing conditions.

2. The method according to claim 1 ,
wherein a maximum speed of the mixing blade during a heating time before reaching T B fulfils at least one condition selected from the group consisting of:
the maximum speed of the mixing blade is at least 20 m/s if a volume of the mixer is more than 40 litres; and
the maximum speed of the mixing blade during the heating time before reaching T B is at most 100 m/s if the volume of the mixer is at most 40 litres.

3. The method according to claim 1 ,
wherein, during the heating phase, at least part of the powder, starting from a temperature that is at least room temperature and at most 60° C. above room temperature, reaches the temperature T B within 20 min.

4. The method according to claim 1 ,
wherein, after reaching the T B and during the holding phase, the temperature is maintained in a range of T B ±5° C. for the holding time.

5. The method according to claim 1 ,
wherein the polymer fulfils at least one condition selected from the group consisting of the conditions:
the polymer is a semi-crystalline polymer and T B is above the heat deflection temperature HDT-A;
the polymer is a semi-crystalline polymer and T B is below the heat deflection temperature HDT-B;
the polymer is a semi-crystalline polymer and T B is at least 20° C. below the melting point T m ;
the polymer is a semi-crystalline polymer, copolymer or polymer blend of polyamide and T B is at least 50° C. below the melting point T m ,
wherein the polymer is a semi-crystalline polymer and wherein T B is at a maximum of 250° C.;
the polymer is a semi-crystalline polymer and wherein T B is at a maximum of 300° C.;
the polymer is a semi-crystalline polymer and T B is at most 50° C. below the glass transition temperature T g of the polymer (determined according to DIN EN ISO 11357);
the polymer is a semi-crystalline polymer and T B is at most 20° C. below the glass transition temperature T g of the polymer (determined according to DIN EN ISO 11357);
the polymer is a semi-crystalline polymer and T B is at most 10° C. below the glass transition temperature T g of the polymer (determined according to DIN EN ISO 11357);
the polymer is a melt-amorphous polymer and T B is at most 20° C. above the glass transition temperature T g and at least 10° C. below the glass transition temperature T g ,
the polymer is a melt-amorphous polymer and T B is at most 20° C. above the glass transition temperature T g and at least 20° C. below the glass transition temperature T g ,
the polymer is a melt-amorphous polymer and T B is above the heat deflection temperature HDT-A (determined according to DIN EN ISO 75); and
the polymer is a melt-amorphous polymer and T B is between the heat deflection temperature HDT-A (determined according to DIN EN ISO 75) and the heat deflection temperature HDT-B (determined according to DIN EN ISO 75).

6. A method according to claim 1 , wherein the at least one heat treatment further includes, after the T B heat treatment, a T N heat treatment that exposes the powder to a temperature T N by heating the powder for a period of at least 30 min and/or at most 30 hours.

7. The method according to claim 6 , wherein the T N heat treatment is associated with one or more of the conditions, each compared to the value of the corresponding parameter before the further step, selected from the group consisting of the conditions:
increase of the bulk density of the powder;
improve

Assignees

• Eos Gmbh Electro Optical Systems

Inventors

• Pfister Andreas
• Gersch Mandy
• Froehlich Daniel
• Galitz Verena
• Fischer Sybille

Classifications

• B29K2077/00

  Use of {PA, i.e.} polyamides, e.g. polyesteramides {or derivatives thereof}, as moulding material · CPC title

• B29K2071/00

  Use of polyethers {, e.g. PEEK, i.e. polyether-etherketone or PEK, i.e. polyetherketone or derivatives thereof}, as moulding material · CPC title

• B29K2023/12

  PP, i.e. polypropylene · CPC title

• B29B9/16

  Auxiliary treatment of granules · CPC title

• B29B7/826

  Apparatus therefor · CPC title