Fireproofing polyamide powders and their use in a sintering process

Abstract

A subject-matter of the invention is the use of a polyamide powder possessing a fireproofing property in a process for the manufacture of an object made of polyamide by sintering this powder using radiation, the said powder comprising, by weight, 2 to 40% of at least one flame retardant for respectively 98 to 60% of at least one polyamide, the flame retardant being a blend of at least one organic phosphinate of a metal and of at least ammonium polyphosphate.

Description

[0001] This application claims benefit, under U.S.C. §119 or §365 of French Application Number 04.08016, filed Jul. 20, 2004; and U.S. 60 / 616,363 filed Oct. 6, 2004.FIELD OF THE INVENTION [0002] The present invention relates to fireproofing polyamide powders and to their use in a sintering process, for example a process for sintering under the action of radiation, such as a laser beam. The invention relates to compositions based on fireproofing powders (for example formed of polyamide 11 or 12) which are compatible with the technique for processing by sintering, for example, under a laser beam. The object is to develop materials which have a good performance with regard to fire resistance without this being made at the expense of the other performance characteristics of the material (viscosity / rheology / flow which are suitable for the targeted application, satisfactory level of mechanical properties) and which can be converted by a sintering technique which uses radiation, more parti...

AI Technical Summary

Benefits of technology

[0024] It is also possible to add the flame retardant to the molten polyamide in a mixing device and to reduce the product obtained to the powder form but with, in this case, the risk of a fall in the enthalpy of fusion and the consequences mentioned above during the conversion of the powder by sintering technology.

Problems solved by technology

This is because, at the time to immediately after the action of the laser beam, the temperature of the sample is greater than the crystallization point (CP) of the powder but the introduction of a fresh, colder, powder layer causes the temperature of the component to rapidly fall below the CP and brings about deformations.

This is because, if the enthalpy of fusion is too low, the energy introduced by the laser is sufficient to sinter by thermal conduction the powder particles close to the growing walls but the geometrical precision of the component is no longer satisfactory.

It has also been discovered that the usual fireproofing agents for polyamides are not all suitable.

For example, melamine cyanurate is not suitable.

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