FLAME RETARDANT POLYAMIDES AND COPOLYAMIDES FOR 3D PRINTING

Abstract

Process for the preparation of flame-retarded parts by powder bed fusion, in which the powder comprises at least one polyamide and at least one flame-retardant agent of cyclic phosphonate ester type.

Claims

1. A process for the preparation of flame-retarded parts by powder bed fusion, in which the powder comprises at least one polyamide and/or copolyamide and at least one flame-retardant agent of cyclic phosphonate ester type, in which the flame-retardant agent of cyclic phosphonate ester type is of general formula (I): ##STR00006## in which: j, k, l and m, which are identical or different, represent an integer from 1 to 3; A.sup.1 and A.sup.2, which are identical or different, represent an alkyl group of 1 to 4 carbon atoms or an aryl group of 5 to 7 carbon atoms.

2. The process as claimed in claim 1, in which the process is a 3D printing process and the powder is a powder for 3D printing.

3. The process as claimed in claim 1, in which the process is a process for 3D printing by laser sintering of the powder.

4. The process as claimed in claim 1, in which the polyamide is selected from the group consisting of polyamide 6 (PA 6), polyamide 66 (PA 66), polyamide 610 (PA 610), polyamide 612 (PA 612), polyamide 11 (PA 11) and polyamide 12 (PA 12).

5. The process as claimed in claim 1, in which the polyamide is PA 11.

6. The process as claimed in claim 1, in which the flame-retardant agent of cyclic phosphonate ester type is of general formula (II): ##STR00007## in which A.sup.1 and A.sup.2, which are identical or different, represent an alkyl group of 1 to 4 carbon atoms or an aryl group of 5 to 7 carbon atoms.

7. The process as claimed in claim 1, in which the flame-retardant agent of cyclic phosphonate ester type is of following formula (III): ##STR00008##

8. The process as claimed in claim 1, in which the powder comprises from 5% to 40% by weight, with respect to the total weight of the powder, of the flame-retardant agent of cyclic phosphonate ester type.

9. The process as claimed in claim 1, in which the powder comprises at least 50% by weight of polyamide and/or copolyamide, with respect to the total weight of the powder.

10. The process as claimed in claim 1, in which the powder comprises at least one other additive selected from the group consisting of a synergist of the flame-retardant agent of cyclic phosphonate ester type, of a pigment, of a dye, of a plasticizer, of an antioxidant, of a pourability agent and of a UV absorption agent.

11. A powder intended for the preparation of flame-retarded parts by powder bed fusion, comprising at least one polyamide and/or copolyamide, and at least one flame-retardant agent of cyclic phosphonate ester type, in which the flame-retardant agent of cyclic phosphonate ester type is of general formula (I): ##STR00009## in which: j, k, l and m, which are identical or different, represent an integer from 1 to 3; A.sup.1 and A.sup.2, which are identical or different, represent an alkyl group of 1 to 4 carbon atoms or an aryl group of 5 to 7 carbon atoms.

12. The powder as claimed in claim 11, wherein the powder is configured for a 3D printing process.

13. The powder as claimed in claim 11, in which the flame-retardant agent of cyclic phosphonate ester type is of general formula (II): ##STR00010## in which A.sup.1 and A.sup.2, which are identical or different, represent an alkyl group of 1 to 4 carbon atoms or an aryl group of 5 to 7 carbon atoms ##STR00011##

14. The powder as claimed in claim 11, in which the powder comprises from 5% to 40% by weight, with respect to the total weight of the powder, of the flame-retardant agent of cyclic phosphonate ester type.

15. The powder as claimed in claim 11, in which the powder comprises at least 50% by weight of polyamide and/or copolyamide, with respect to the total weight of the powder.

16. The powder as claimed in claim 11, in which the powder comprises at least one other additive selected from the group consisting of a synergist of the flame-retardant agent of cyclic phosphonate ester type, of a pigment, of a dye, of a plasticizer, of an antioxidant, of a pourability agent and of a UV absorption agent.

17. The use of a powder as defined in claim 11, in a powder bed fusion process, in order to produce a flame-retarded part.

18. A process for the preparation of a powder as defined in claim 11, comprising the blending of at least one polyamide and/or copolyamide and of at least one flame-retardant agent of cyclic phosphonate ester type, in which the flame-retardant agent of cyclic phosphonate ester type is of general formula (I): ##STR00012## in which: j, k, l and m, which are identical or different, represent an integer from 1 to 3; A.sup.1 and A.sup.2, which are identical or different, represent an alkyl group of 1 to 4 carbon atoms or an aryl group of 5 to 7 carbon atoms.

19. The process as claimed in claim 18, in which the blending is carried out by dry blending.

Description

DESCRIPTION OF THE FIGURES

[0077] FIG. 1 is a photograph of a part obtained by 3D printing starting from a powder according to the invention.

[0078] FIG. 2 is a photograph of a part obtained by 3D printing starting from a comparative powder.

[0079] The invention will be further clarified, in a nonlimiting way, using the examples and figures which follow.

EXAMPLE

Example 1

[0080] A powder according to the Invention is produced by dry blending (using a Henschel blender) 33% by weight with respect to the total weight of the powder, of polyamide 11 (Rilsan Invent Natural (RIN), Arkema) and 17% by weight with respect to the total weight of the powder, of flame-retardant agent of cyclic phosphonate ester type of following formula (III):

##STR00005##

[0081] A comparative powder is produced which comprises 80% by weight with respect to the total weight of the powder, of polyamide 11 (Rilsan Invent Natural (RIN), Arkema) and 20% by weight with respect to the total weight of the powder, of flame-retardant agent of melamine polyphosphate type (Melapur™ 200, BASF).

[0082] The powders are used to feed a Formiga® P100 (Eos) 3D printer and to print a part of bartype having the following dimensions: length 127 mm, width 12.7 mm and thickness 2.5 mm.

[0083] Photographs of the parts obtained are presented in FIG. 1 (powder according to the invention) and in FIG. 2 (comparative powder).

[0084] It is observed that while the powder according to the Invention makes it possible to obtain a perfectly smooth part the part obtained with the comparative powder exhibits coalescence problems. The comparative powder is thus unsuitable for use for 3D printing.

Example 2

[0085] Tests were carried out with a commercial flame-retardant agent Technirez® FR-001, exhibiting a viscous liquid appearance, which has the same molecule as the flame-retardant agent Antiblaze 1045®.

[0086] Test 1: The flame-retardant agent Technirez® FR-001 was introduced into the polyamide powder by means of a Henschel blender.

[0087] A very fluffy powder is obtained. It is impossible to use it in the 3D printing machine, i.e. the part sintering could not be carried out.

[0088] Test 2: The flame-retardant agent Technirez® FR-001 is preheated at 70° C. before introducing it into a Henschel blender with the polyamide powder with stirring.

[0089] A very fluffy powder is obtained. It is impossible to use it in the 3D printing machine, i.e. the part sintering could not be carried out.

Example 3

[0090] The part obtained from the powder according to the invention as defined in example 1 was tested according to the standard UL 94V.

[0091] Briefly, according to this standard, the length of the sample is 127 mm and its width is 12.7 mm. Its thickness must not exceed 12.7 mm. The sample is fixed at ¼ from its upper end in the vertical position. A metal net covered with absorbent cotton is positioned at 305 mm under the sample. The burner is adjusted in order form a blue flame of 19 mm which rises in temperature from 100 to 700° C. in 44±2 seconds. This flame is directed from below over the lower edge of the plastic sample at a distance of 9.5 mm. It is applied for 10 seconds then removed. The combustion time of the sample is measured. As soon as combustion has halted, the flame is reapplied fir 10 seconds, immediately removed, the combustion time and the glowing time are again measured. The complete test is carried out on five samples.

[0092] The material tested is classified UL 9.4 V-0 if:

[0093] A) NO of the five samples burns for more than 10 seconds after the flame of the burner has been removed.

[0094] B) The total combustion time over the 10 tests does not exceed 50 seconds.

[0095] C) None of the samples tested burns, either with a flame Or by incandescence, as far as the holding jaw

[0096] D) No blowing drop, which can ignite the cotton cloth placed below, falls from any sample.

[0097] E) No sample exhibits a glowing time exceeding 30 seconds.

[0098] The material tested is classified as LI 94 V-1 if:

[0099] A) None of the five samples burns for more than 30 seconds after the flame of the burner has been removed.

[0100] B) The total combustion time over the 10 tests does not exceed 250 seconds.

[0101] C) None or the samples tested burns, either with a flame or by incandescence, as far as the holding jaw.

[0102] D) No glowing drop, which can ignite the cotton cloth placed below, falls from any sample.

[0103] E) No sample exhibits a glowing time exceeding 60 seconds.

[0104] The material tested is classified as UL 94 V-2 if:

[0105] A) None of the five samples burns for more than 30 seconds after the flame of the burner has been removed.

[0106] B) The total combustion time over the 10 tests does not exceed 250 seconds.

[0107] C) None of the samples tested burns, either with a flame or by incandescence, as far as the holding jaw.

[0108] D) A few fragments may become detached from the sample tested burning temporarily, and some of which may ignite the cotton cloth placed below.

[0109] E) No sample exhibits a glowing time exceeding 60 seconds.

[0110] Results of tests according to the standard UL 94 V: The part according to the invention is classified V-0 according to the standard UL 94 measured with a thickness of 1.3 mm on the samples.

[0111] By comparison, a part with the same dimensions obtained with the powder FR-106 (Advanced Laser Materials, ALM) of flame-retarded polyamide for 3D printing based on PA 11 (PA D80-ST, ALM) and comprising a flame-retardant agent of brominated polyacrylate type (FR-1025, ALM) was tested and is classified as V-2 according to the standard UL 94, measured with a thickness of 2.5 mm on the samples.

[0112] The mixture according to the invention is suitable for obtaining parts of good quality in 3D printing while conferring on them a flame retardancy equivalent to or superior to that obtained according to the state of the art.

Example 4

[0113] In addition, the mechanical properties of maximum stresses and of elongation at break of the parts obtained using the powder according to the invention are equivalent to those of parts obtained with the comparative powder FR-106 comprising a halogenated flame-retardant agent. An improvement in the Young's modulus, measured according to the standard ISO 527-2: 2012-1A is even noted, with per in 2000 MPa for the parts of the invention versus 1750 for the parts Obtained with the comparative powder FR-106.

[0114] The present invention thus provides a powder devoid of halogenated additives, which is easy to prepare and to use in 3D machines, making it possible to manufacture a part having a better flame-retardant property while retaining the mechanical properties.