DE102019219086A1 - Material for processing in the selective laser sintering process, use of the material and moldings made from it - Google Patents

Abstract

The invention relates to a material as a starting material for the SLS process, which, in addition to special, required flame retardant properties, gives a molded article produced therefrom in the SLS process as well as optimal mechanical properties such as elongation at break, tensile strength and / or elasticity. The invention also relates to a flame-retardant molded body which can be produced using the selective laser sintering process, or SLS process for short, and which in particular meets the fire protection requirements of DIN 45545. The invention makes it possible for the first time to use an amorphous compound, obtainable by compounding amorphous polymers, to produce an amorphous powdery starting material for use in an SLS powder bed to produce a molded body with partially crystalline components. By processing the powdery starting material in the SLS process, flame-retardant moldings, as they can be part of the interior and / or exterior cladding of vehicles, rail vehicles, ships, aircraft, but also part of buildings, housings, and or other products.

Description

The invention relates to a material as a starting material for the SLS process which, in addition to special, required flame retardant properties, gives a molded article produced therefrom in the SLS process as well as optimal mechanical properties such as elongation at break, tensile strength and / or elasticity. The invention also relates to a flame-retardant molded body which can be produced using the selective laser sintering process, or SLS process for short, and which in particular meets the fire protection requirements of DIN 45545.

The material according to the invention is used, for example, to produce a molded body that is suitable for the mobility industry, that is, it forms part of the interior lining of a vehicle, such as a rail vehicle, automobile or aircraft in particular. In addition to pure flame retardancy, the aspect of protecting passengers and / or staff from smoke and / or toxic gases in the event of a fire must also be taken into account, as specified in DIN standard EN 45545.

The SLS process refers to a process in which plastic in powder form is preferably completely melted in layers in a construction space, there in the so-called powder bed, and / or melted in the thermoplastic edge areas, in particular without the use of binders, but only through Irradiation with a laser, resulting in a molded body with high density after solidification.

In an SLS process, the powdery starting material _{is melted using a laser, for example a CO 2} laser, an Nd: YAG laser and / or another laser, in accordance with a specified component plan in the powder bed. A defined temperature prevails in the installation space. The temperature range suitable for this is specified via the hot crystallization point and the melting point of the powdery starting material.

During the SLS process, there is an increased temperature of 150 ° C or more in the installation space, but in particular the temperature can also be up to 380 ° C.

Semi-crystalline plastics are particularly suitable for processing / use in the selective laser sintering process (SLS process), but have poor fire protection properties. By adding fire protection additives, the fire protection properties can be improved, which, however, significantly affects the mechanical properties of the moldings produced in the SLS.

The disadvantage of the previously known technology is in particular that the so-called "old powder" remaining in the powder bed after production, at least 50% by weight, has to be mixed with fresh powder that has not yet been in the installation space, so that the mechanical properties, in particular also the dimensional stability of the manufactured molded body and, last but not least, the surface quality - keyword "orange peel" of the flame-retardant manufactured molded body is preserved.

Tests have shown that when - PEK - "polyether ketone" is used in a "partial crystallinity" of approx. 20% to 60% mass fraction crystalline, the old powder even has to be disposed of 100% after an SLS process has been carried out (company EOS, PEK, "PEEK HP3").

State of the art, for example the DE 10 2017 203 962 , is that amorphous plastics are fundamentally unsuitable for processing in the SLS process, because their softening and / or melting and / or solidification properties are for the SLS process, in which short-term melting, followed by a short-term solidification entrance, not suitable.

From the DE 10 2017 203 962 is a material for use in the SLS process, a compound of at least a first partially crystalline plastic, selected from the group of polyaryletherketones, -PAEK-, polyetherketoneketone, -PEKK-polyetherketone -PEK-, polyetheretherketone -PEEK- and a second amorphous plastic, selected from the group consisting of polyetherimide - PEI-, polyethersulfone -PES-, polyphenylene sulfone -PPSU- and / or polysulfone -PSU-, all derivatives of the compounds mentioned being included and in the compound both the first and the second plastic in turn as a mixture may exist, known. In the case of this powder, a significant increase in the recyclability of the old powder remaining in the powder bed is already determined without any measurable impairment of a molded body produced with it.

When processing a material into an SLS-compatible plastic compound according to the state of the art - as it is, for example, from the DE 10 2017 203 962 is known - the procedure is that a partially crystalline blend is first mixed with an amorphous blend in order to shift the crystallization point. For this purpose, a partial crystallinity of the mixed blend used of at least 10% up to a maximum of 100% partially crystalline material is required. This blend is compounded and processed into powder, then it becomes like that The powder obtained is filled into an SLS powder bed, from which a shaped body is produced by laser irradiation, which, depending on the composition of the powder, can also exhibit flame-retardant properties.

The disadvantage of the prior art known to date is that at least one starting material for producing the compound must be partially crystalline so that the temperature window for the installation space temperature of the device for performing the SLS process can be determined. However, partially crystalline polymers are expensive to purchase and more complicated to use than amorphous polymers.

After US20150259530 A1 a second polymer is added to the partially crystalline polymer before processing in the SLS process, so that the hot crystallization temperature of the material composed of both polymers is reduced by at least 3 ° C, so that there is an extended temperature window for processing in the SLS process.

Another disadvantage of the state of the art for producing flame-retardant components using the SLS process is the extensive consumption of materials and the lack of sustainability, since usually only around 20% of the powder present in the powder bed is actually processed into a component. Apart from this, the additional process steps for disposal and the costs incurred, as well as the additional material consumption, are disadvantageous in the known state of the art for the production of flame-retardant plastic components in the SLS process.

The poor recyclability of the powder is largely due to the partial crystallinity of the powder stored in the powder bed of the installation space. According to previous technical and scientific knowledge, a powder with at least a partially crystalline portion, possibly also in a blend with amorphous powders, is basically present in the powder bed for a successful production of a component in the SLS process. This is particularly because a process temperature window for the powder in the powder bed is defined for processing in the SLS process, within which the powder is melted and re-solidified by the laser beam ( 1 ). This temperature window usually begins at the melting point of the powder. Amorphous powders do not have such a melting point and therefore no SLS temperature windows can be defined for amorphous powders, so that amorphous powders have not been used for the SLS process up to now.

The known powdery starting materials always result in a large number of rejects in the SLS process because, due to the high proportions of partially crystalline polymer in the material of the powder bed and the high installation space temperature, the unused powder of the powder bed cannot be used, or only in small proportions, for another SLS process .

The object of the present invention is therefore to provide a material for the production of a powder for use in the SLS process that leaves little scrap in the processability of the SLS process and at the same time is suitable for the production of flame-retardant components in the SLS process.

The present invention therefore relates to a material for the production of a powdered starting material for use in an SLS powder bed, at least one first polymer, which is an amorphous polyaryletherketone and a second polymer, which is an amorphous polymer from the group of intrinsically flame-retardant thermoplastics, containing, wherein the first and second polymer in the material are each present in an amount of 5% by weight to 95% by weight, based on the polymer substance of the powdery starting material. In addition, the subject matter of the invention is the use of the material in the SLS process, in particular in the SLS process at an elevated installation space temperature, e.g. preferably at least 150 ° C. Finally, a molded body, in particular a flame-retardant molded body with partially crystalline components, can be produced by processing the material in the SLS process at an increased installation space temperature.

The general knowledge of the invention is that although amorphous polymers do not show discrete temperature windows as clearly as partially crystalline polymers show, they do have a glass transition point from which a minimum process temperature can be derived. In addition, it could be shown that despite the lack of partial crystallinity due to the SLS process, carried out on amorphous starting material, a flame-retardant molded body with demonstrably partially crystalline proportions can be produced.

With the SLS procedure - as in 1 shown - a processing window for a temperature range in the installation space of an SLS device is derived from a hot crystallization temperature and a melting temperature.

1 shows a typical processing window in the SLS process using the example of the partially crystalline material PA12. In the case of partially crystalline materials, both a hot crystallization temperature and a cold crystallization temperature are measured.

In the present case, the principle of process-induced morphology transformation is used, wherein at least two amorphous polymeric compounds are compounded with one another. The resulting compound clearly shows no partially crystalline components. In further pulverization measures, an amorphous powder is created from this, which likewise does not contain any partially crystalline components, but is present entirely as an amorphous powder.

By introducing this amorphous powdery starting material into the powder bed of an SLS device, a morphology transformation is implemented in the melt through the heat exposure in the installation space in conjunction with the laser exposure, so that a molded body with partially crystalline components can be produced using the SLS process.

The surrounding powder, which has not been exposed to the laser, i.e. the residual and / or old powder, remains in the amorphous morphology and, in contrast to known powders with partially crystalline components in the powder bed, does not show any significant signs of aging, but can be reused without any problems.

The molded bodies produced also have high fire protection properties and, at the same time, good and adequate mechanical properties, dimensional accuracy and good surface quality.

“Compounding” is understood here when a material that comprises at least two different amorphous polymers, the compound partner, comprises in at least one processing and / or compounding step by melting the at least one polymer (polymer or polymer mixture) into a polymer matrix homogeneous and uniform new material is compounded. The compound can of course comprise further polymers and / or polymer mixtures and / or further additives such as additives, fillers and the like for producing the shaped body.

In the present case, “material” is understood to mean the material according to the invention, comprising at least two amorphous polymer components, one of which comprises an intrinsically flame-retardant thermoplastic polymer. The two polymers are preferably present in a ratio of 95: 5% by weight to 5:95% by weight.

After compounding, this material is used to produce a powder which can be used in the SLS process for the production of moldings, in particular intrinsically flame-retardant moldings according to DIN 45545.

In the present case, “amorphous” is a polymer in which no more than 10% by weight of crystalline components are present in the solid of the polymer. This condition is generally verified by a differential scanning calorimetry - "DSC" measurement, which is suitable for determining the melting and / or glass transition temperatures of plastics. The amorphous powder in question here shows a glass transition region in the DSC, but neither post-crystallization nor a melting range.

The first polymer is at least one amorphous polyaryletherketone “PAEK”, such as, for example, a polyetherketoneketone PEKK, polyetherketone PEK, polyetheretherketone PEEK. These polymers can be used individually and in any desired mixtures and combinations as the first amorphous polymer. These PAEKs are distinguished by the fact that when they are processed in the SLS process at an increased installation space temperature, for example at least 150 ° C., they result in a molded body with demonstrable partial crystallinity.

PEKK is particularly preferred, which has an amorphous character and retains this in the compound / powder until SLS processing. It is also not found in the DSC during the second heating - see also 6th - a melting peak.

The second polymer is at least one amorphous polymer from the group of intrinsically flame-retardant thermoplastics, for example selected from the group of the following polymers: polyetherimide “PEI”, polyether sulfone “PESU”, polyphenylene sulfone “PPSU”, and / or polysulfone “PSU”. These polymers can also be used again individually and in any desired mixtures and combinations as the second amorphous polymer.

The powdery starting material for the SLS process from these two polymers, optionally with additives and / or other polymers, can be used in the SLS powder bed with high resistance of the powder stored in the installation space but not exposed to laser radiation.

The term “additives” includes, on the one hand, process-improving additives, such as for flowability, these are at least two amorphous polymers in an amount well below 5% by weight, mostly 1 to 2% by weight, based on 100 parts by weight of the powdery starting material comprehensive, added.

On the other hand, this also includes functional additives that change the property profile, these are, for example, in an amount of 5 to 70% by weight such as fillers and reinforcing materials, such as glass fibers, C fibers, etc., which can significantly improve the property profile sequentially, added.

Additives in the form of process-improving additives are in the range of <5% by weight, whereas additives in the form of functional fillers in the range of up to 70% by weight, in particular 5-65% by weight, preferably in the range of approx. 15-30% by weight can be added.

As a result of the compounding, the additives are embedded in a polymer matrix and / or they are added to the powder as a dry mixture directly before application to the powder bed.

Regardless of how, both in the powder of the powder bed and on the finished molded body, the polymer substance can be seen in the form of the polymeric matrix, which is formed from the at least two amorphous polymers in the powdery starting material according to the invention and which are analyzed according to mass and / or weight proportions can. The percentages by weight given in the invention in which the first and second polymer are present relate to this polymer substance.

Example 1:

As in 2 and 3rd shown, in the amorphous powder, shown here in example 1, pure PEI-polyetherimide-amorphous, there is no melting point in the material that would be recognizable as a peak, but “only” a glass transition area, the material is therefore - according to DSC - amorphous .

2 shows the heating, whereas 3rd the cooling curve shows.

The measuring device used for the DSC measurement is a DSC Q100 V9.9 Build 303 from TA “Texas Instruments”, the heating rate being 10K / min.

PEI from Example 1 is an intrinsically flame-retardant, amorphous thermoplastic which, according to the invention, is used with at least one second, polymeric and amorphous substance, a polyaryletherketone, to produce the material.

Example 2: Pure polyether ketone ketone:

4th shows an example of a DSC measurement DSC measuring device 204F1 Phoenix from Netzsch, the same heating rate at 10K / min as in the measurement of Example 1 above, of a polyaryletherketone, here the polyetherketoneketone “PEKK” also present in amorphous form. Commercially available granules were measured. In the second heating, this of course initially shows the glass transition area as in Example 1 “pure PEI” but also in the temperature range up to 350 ° C an amorphous-partially crystalline transition from approx. 220 ° C, T onset 223.4 ° C. This shows the post-crystallization with a seamless melting range.

As can be seen from the measurement, the post-crystallization shows a peak at 244.7 ° C. (onset at 223.4 ° C.) and an enthalpy of -9.4 J / g. The melting range begins smoothly with a peak (?) At 292.0 (onset 274.2 ° C) and a melting enthalpy of 11.2J / g. Since the enthalpy of recrystallization and enthalpy of fusion are almost the same, it is clear that the material was amorphous before melting.

Partially crystalline polymers in the state of maximum achievable partial crystallinity do not show any post-crystallization during the DSC measurements - 1st heating. If they are in a state of partial partial crystallinity, especially in the case of rapid cooling processes, they show post-crystallization during the 1st heating, in an area in which the molecular chains frozen due to the rapid cooling become mobile and join together to form partially crystalline areas. From an energetic point of view, the melting energy consists on the one hand of the energy to "de-partially crystallize" the recrystallized areas again (energy absorption) and on the other hand of the energy to melt the partially crystalline areas that were already present (before the recrystallization). If the amount of post-crystallization enthalpy and melting enthalpy are almost the same, this means that there were no partially crystalline areas before the first melting.

$$rel.Xc\left[\%\right]=\frac{\Delta \text{Hs}-\Delta \text{Hnk}}{\Delta \text{Hs}}\ast 100\%$$

Teilkristallinitätsgrad = (Schmelzenthalpie - Nachkristallisationsentahlpie) / Schmelzenthalpie x max. Teilkristallinitätswert); relativer Teilkrisallinitätswert = Anteil an der maximal erreichbaren TeilkristallinitätThe (partial) degree of crystallinity Xc is usually calculated using the difference between the amounts of melting enthalpy ΔHs and post-crystallization enthalpy ΔHnk, as well as a maximum partial crystallinity value - this includes the measured melting enthalpy ΔHs and an approximated melting enthalpy - one hundred percent crystalline material ΔH0 - to be ΔHs / ΔH0: $$Xc\left[\%\right]=\frac{\Delta \text{Hs}-\Delta \text{Hnk}}{\Delta \text{Hs}}\ast \frac{\Delta \text{Hs}}{\Delta \text{H0}}\ast 100\%$$

$$rel.Xc\left[\%\right]=\frac{\Delta \text{Hs}-\Delta \text{Hnk}}{\Delta \text{Hs}}\ast 100\%$$

Partial crystallinity = (melting enthalpy - post-crystallization enthalpy) / melting enthalpy x max. Partial crystallinity value); relative partial crystallinity value = proportion of the maximum achievable partial crystallinity

The powder grain sizes of the powder produced from the compound for processing in the SLS process are in the range of less than 100 μm customary for the SLS process, in particular in the range from 30 μm to 80 μm, in particular around 50 μm. Powder forms that have a show a certain flowability so that they can be better processed in the powder bed, for example with a doctor blade. For this purpose, according to an advantageous embodiment of the invention, the powder grains are in a rounded shape.

The density of the material used for the preparation of the compound is preferably in the range of 1 g / cm ³ to 2 g / cm ^3, in particular in the range of 1 g / cm ³ to 1.5 g / cm ^3, for example in a PEKK PEI Compound , in which the density of both plastic components is 1.27 g / cm ³ , the percentages by volume correspond to the percentages by weight.

5 shows three DSC measurements of three exemplary materials according to the invention, in the form of their compounds, because there is no homogeneous material but a loose mixture before compounding. Only in the form of the compound does the material show a uniform behavior in the DSC measurement, in particular the heating and cooling curve.

• - Beispiel 3:
  • PEI:PEKK wie 70:30 in 5 der zuoberst liegende Graph
• - Beispiel 4:
  • PEI:PEKK wie 50:50 in 5 der mittlere Graph
• - Beispiel 5:
  • PEI:PEKK wie 30:70 in 5 der unterste Graph Alle Graphen aus der 5, jeweils gemessen mit DSC-Messgerät 204F1 Phoenix der Firma Netzsch, alle Messung bei der gleichen Heizrate von 10K/min.

Here the DSC measurement of the compounds according to Examples 3 to 5, these show the ratio of the two amorphous starting materials PEI and PEKK

• - Example 3:
  • PEI: PEKK like 70:30 in 5 the top graph
• - Example 4:
  • PEI: PEKK as 50:50 in 5 the middle graph
• - Example 5:
  • PEI: PEKK as 30:70 in 5 the bottom graph All graphs from the 5 , each measured with a DSC measuring device 204F1 Phoenix from Netzsch, all measurements at the same heating rate of 10K / min.

These graphs all show neither melting point nor crystallization point, but only a glass transition area, which is clear evidence that the compounded material is amorphous.

• Beispiel 5, oberster Graph 6: Heizrate 20K/min
• Beispiel 5, mittlerer Graph 6: Heizrate 10K/min
• Beispiel 5, unterster Graph 6: Heizrate 5K/min

The compound of Example 5 was also subjected to a check by means of a further three DSC measurements of the same device, but with changed heating rates. The result is in 6th evident. 6th shows the second heating. The three graphs shown show from top to bottom:

• Example 5, top graph 6th : Heating rate 20K / min
• Example 5, middle graph 6th : Heating rate 10K / min
• Example 5, bottom graph 6th : Heating rate 5K / min

The measurement of the middle graph corresponds to from 6th the measurement of the bottom graph of the 5 because both example 5 show a heating rate of 10K / min.

The invention makes it possible for the first time to use an amorphous compound, obtainable by compounding amorphous polymers, to produce an amorphous powdery starting material for use in an SLS powder bed to produce a molded body with partially crystalline components. By processing the powdery amorphous starting material in the SLS process at increased installation space temperature, flame-retardant molded bodies, such as those used in the interior and / or exterior cladding (s) and / or equipment (s) of vehicles, rail vehicles, ships, and aircraft will be can, but can also be part of buildings, housings, and / or other products.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102017203962 [0009, 0010, 0011]
• US 20150259530 A1 [0013]

Claims (15)

Material for the production of a powdery starting material for use in an SLS powder bed, at least one - First polymer, which is an amorphous polyaryletherketone present and a - Second polymer, which is an amorphous polymer from the group of intrinsically flame-retardant thermoplastics, containing the first and second polymer in the material each in an amount of 5% by weight to 95% by weight, based on the polymer substance of the powdered starting material produced therefrom, which the polymer matrix forms, are present. Material after Claim 1 , which in the DSC measurement shows a glass transition range, but neither post-crystallization nor a melting range. Material according to one of the Claims 1 or 2 , which has as a first polymer at least one amorphous polyaryletherketone “PAEK”, such as a polyetherketoneketone PEKK, polyetherketone PEK, polyetheretherketone PEEK. Material according to one of the preceding claims, wherein the second polymer is selected from the group of the following polymers: polyetherimide “PEI”, polyether sulfone “PESU”, polyphenylene sulfone “PPSU”, and / or polysulfone “PSU”. A material according to any preceding claim comprising additives. A material according to any one of the preceding claims which has a ratio of first to second polymer in the range of 30:70 to 70:30 parts by weight. A material according to any one of the preceding claims which has a ratio of first to second polymer in the range of 40:60 to 60:40 percent by weight. Material according to one of the preceding claims, wherein the pulverulent material has particles with a grain size in the range below 100 µm, in particular in the range between 30 µm and 80 µm. Material according to any one of the preceding claims, wherein the powdery starting material comprises rounded particles. Use of an amorphous powder according to one of the Claims 1 to 9 for processing in the SLS process, in particular an SLS process in an installation space with a temperature of over 150 ° C. Use after Claim 10 for the production of a molded body with partially crystalline parts in the SLS process. Flame-retardant molded body, obtainable by processing a powdery and amorphous starting material from a material according to one of the Claims 1 to 9 in the SLS procedure. Molded body according to Claim 12 that is part of an interior and / or exterior paneling of a vehicle, a rail vehicle, a ship and / or an aircraft. Molded body according to Claim 12 that is part of the interior and / or exterior equipment of a vehicle, a rail vehicle, a ship and / or an aircraft. Molded body according to Claim 12 that is part of a building, a product and / or a housing.

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