Powdery composition of a polymer and a flameproofing agent containing ammonium polyphosphate, method for the production thereof, and moulded body produced from said powder

European).

OK II-12 / P21737PL00

EP 1 648 958 B1

Powder composition of polymer and flame retardant containing ammonium polyphosphate, method of its production and molded product made from this powder

The invention relates to a polymeric powder having at least one polymer and at least one flame retardant containing ammonium polyphosphate, and relates to a process for the production of this powder and to a molded article produced by layering and fusing this powder.

Quick prototype preparation is one of the tasks frequently asked recently. Due to their flexibility, especially those methods which focus on powdered material and selectively fuse or bond are in the spotlight.

Selective laser sintering is a way that is particularly well suited for rapid prototyping. In this method, the plastic powder is selectively irradiated briefly with a laser beam, as a result of which the powder particles which the laser beam hits are fused. The molten particles merge into each other and quickly solidify again into a solid mass. By re-irradiating the newly applied layers, this method can easily and quickly produce three-dimensional solids with complex geometry.

The method of laser sintering (rapid prototyping) to obtain molded articles from powdered polymers is described in detail in US 6,136,948 and WO 96/06881 (both by DTM Corporation). A lot of polymers and copolymers such as polyacetate, polypropylene, polyethylene, ionomers and polyamide can be used for this implementation.

In practice, in the case of laser sintering, primarily polyamide 12 (PA 12) powder has proven its worth in the production of molded products, especially technical structural components. The elements made of the PA 12 powder meet the high demands that it places on the mechanical load, and thus in their properties reach particularly close to subsequent serial elements, which are obtained by extrusion or injection molding.

In addition, medium-grained PA 12 powder is well suited (d₅₀) 50-150 μη, such as, for example, obtained according to DE 197 08 946 or DE 44 21 454. Preferably, polyamide 12 powder with a melting point of 185-189 ° C, with a melting enthalpy of 112 ± 17 J / is used. at a pour point of 139-143 ° C, as described in EP 0 911 142.

Other well-suited methods are the SIV-Method as described in WO 01/38061 or EP 1 015 214. Both methods operate by flat infrared heating to melt this powder. The melting selectivity in the first method is achieved by applying the inhibitor, in the second method through the mask. A further method that has found great acceptance in the commercial market is three-dimensional printing according to EP 0 431 924; there formed molded products by curing the binder selectively applied to the powder layer. In this case, the energy needed for melting is selectively fed through a microwave generator and selectivity is achieved by applying a susceptor.

Powdered substrates, especially polymers or copolymers, preferably selected from polyesters, polyvinyl chloride, polyacetals, can be used for the mentioned rapid prototyping (Rapid-Prototyping) or rapid production method (Rapid-Manufacturing-Verfahren) (RP-or RP-method). polypropylene, polyethylene, polystyrene, polycarbonate, poly- (N-methylmethacrylamides) (PMMI), polymethyl methacrylate (PMMA), ionomer, polyamide, copolyesters, copolyamides, terpolymers, acrylonitrile butadiene styrene (ABS) copolymers or mixtures thereof.

Despite the good properties of already known polymer powders, molded products made with such powders still have some disadvantages. Inflammability and flammability are particularly unfavorable for currently used polymer powders. This is currently thwarting the use of the above discussed methods for use in small series in aircraft production.

The object of the present invention was therefore to provide a polymer powder that would allow poorer ignitability of the components made therefrom by one of the methods discussed above.

It has now surprisingly been found, as described in the claims, that by adding flame retardants containing ammonium polyphosphate to polymers or copolymers, it is possible to produce powder compositions (powders) from which products formed by means of a layered process can be produced in which the selective areas are melted or with it binds itself, which molded products are clearly less inflammable and flammable than those formed from traditional polymeric powders.

The subject of the present invention is therefore a powdered kit, especially construction powder or powder for rapid prototype creation and powder for rapid production (powder-RP / -RM) for rapid prototype creation or rapid production applications for processing in a method of building layers of three-dimensional objects in which selective parts of this powder are bound together, which set is characterized by that this powder exhibits at least one polymer and at least one flame retardant exhibiting ammonium polyphosphate, and a maximum particle size <150 μπι.

Also the subject of the present invention is a method for producing a powder according to the invention (powder composition) which is characterized in that a powdered blend of a polymer and a flame retardant having ammonium polyphosphate is produced.

In addition, the subject of the present invention is the use of the powder according to the invention for the production of molded articles by means of layers of a selectively binding powder working process and is a molded article produced by means of building layers of three-dimensional objects in which the selective parts of the powder are bound together and which is characterized by that it exhibits at least one flame retardant exhibiting ammonium polyphosphate and has at least one polymer.

The powder according to the invention has the advantage that from it, by means of one of the above-described methods-RP or -RM for building three-dimensional objects in layers, in which the selective parts of the powder used are combined with each other, it is possible to produce molded products that exhibit poorer flammability and inflammability. At the same time, the mechanical properties of molded articles are substantially maintained. Thus, the fields of application are opening up which up to now have not been possible due to poor classification in terms of flammability. It was particularly surprising that if the minimum content of the flame retardant containing ammonium polyphosphate was observed in the powder, classification of the finished molded product even at the V0 grade according to UL94 (Underwriters Laboratories Inc., test method 94V) could be achieved.

In addition, it was surprisingly found that molded products made from the powder of the invention exhibit consistently good or even improved mechanical properties, in particular with respect to elastic modulus, tensile strength and density. Also, the appearance of these molded articles shows good quality, for example good retention of exact dimensions and surface quality.

The powder according to the invention and the method of its preparation are described below without the intention of limiting it to this invention.

The construction powder or powder kit for processing according to the invention in a method for building layers of three-dimensional objects in which the selective parts of this powder bind together, is distinguished by the fact that the powder has at least one polymer and at least one flame retardant exhibiting ammonium polyphosphate and maximum particle size <150 μη, preferably 20-100 μη. The powder in these methods is preferably bound by an energy supply, particularly preferably by heat, wherein the particles are bound together by fusion or sintering. Similarly, this powder can be used in methods in which the particles are bound by chemical reaction with each other or with a binder, or by physical means, preferably drying or gluing. Details for individual methods can be taken from the above-mentioned descriptions.

The polymer as well as the flame retardant according to the invention may be present as a mixture of the given powders or as a powder in which the majority of the grains or each grain has both a polymer and a flame retardant. In the case of such powders, the flame retardant may be uniformly dispersed in these particles or also in the middle of the particle or on the surface of the particle.

As a polymer, this powder preferably has a homo- or copolymer selected from polyesters, polyvinyl chloride, polyacetals, polypropylene, polyethylene, polystyrene, polycarbonate, poly (N-methylmethacrylamide) (PMMI), polymethyl methacrylate (PMMA), ionomer, polyamide, copolyesters, copolyamides, terpolymers, acrylonitrile butadiene styrene (ABS) copolymers or mixtures thereof. Particularly preferably the powder according to the invention contains a polymer which has a melting point of 50-350 ° C, preferably 70-200 ° C.

The polymers present in the powder according to the invention can be prepared in particular by milling, precipitation and / or anionic polymerization or a combination thereof, or by subsequent fractionation.

The powder according to the invention, especially when the powder is to be used for selective laser sintering, preferably has at least one polyamide. As polyamide, the powder according to the invention preferably has a polyamide which has at least 8 carbon atoms per one carbonamide group. Preferably, the powder of the invention preferably has at least one polyamide which has 9 or more carbon atoms per one carbonamide group. Very preferably, this powder has at least one polyamide selected from polyamide 612 (PA 612), polyamide 11 (PA 11) and polyamide 12 (PA 12) or copolyamides based on the aforementioned polyamides. The powder according to the invention preferably has unregulated polyamide.

Particularly suitable for laser sintering is sintered polyamide 12 powder, which has a melting point of 185-189 ° C, preferably 186-188 ° C, a melting enthalpy of 112 ± 17 J / g, preferably 100-125 J / g and a pour point of 133-148 ° C, preferably 139-143 ° C. The process for producing polyamide powder, which is the basis for the sintered powders according to the invention, is generally known and can be taken for PA 12 e.g. of DE 29 06 647, DE 35 10 687, DE 35 10 691 and DE 44 21 454, the content of which is intended to belong to the content of the disclosure of the present invention. The required polyamide granules can be purchased from various manufacturers, for example, polyamide 12 granules are offered by Degussa AG under the trade name VESTAMID.

Also particularly well suited is polyamide 12, which has a melting point of 185-189 ° C, preferably 186-188 ° C, a melting enthalpy of 120 ± 17 J / g, preferably 110-130 J / g and a pour point of 130-140 ° C, preferably 135-138 ° C and, above all, also has an crystallization temperature of 135-140 ° C after aging. The determination of these measured values ​​was carried out, as described in EP 0 911 142, by thin layer chromatography (DSC).

For a method for producing three-dimensional objects that do not work with a laser, a powder that exhibits a copolymer, especially a copolyamide, is particularly well suited.

The powder according to the invention, with respect to the sum of the powdered polymers present, primarily has 5-50% by weight of a flame retardant containing ammonium polyphosphate, preferably 10-40% by weight of a flame retardant containing ammonium polyphosphate, particularly preferably 20-35% by weight of flame retardant containing ammonium polyphosphate and extremely preferably 23-34% by weight of a flame retardant containing ammonium polyphosphate. The ranges given here apply to the entire content of the flame retardant containing ammonium polyphosphate powder, with powder being understood as consisting of all ingredients.

The powder according to the invention may show a mixture of a flame retardant containing ammonium polyphosphate and polymeric particles, or also have polymeric particles or a polymer powder which exhibit a fire retardant containing ammonium polyphosphate. In the case of a flame retardant containing ammonium polyphosphate, below 5% by weight based on the total, the components of the amount constituted clearly reduce the desired effect of difficult flammability and incombustibility. In the case of a flame retardant containing ammonium polyphosphate, above 50% by weight based on the total, mechanical components such as e.g. elongation at break of molded articles made of such powders.

If the powder has a mixture of polymeric particles and a flame retardant containing an ammonium polyphosphate, the polymeric particles have a maximum particle size of 150 μπι, preferably an average particle size of 20-100 μη and particularly preferably 45-80 μη. The flame retardant containing ammonium polyphosphate has a particle size that is below the average particle size d₅₀polymer particles or powders by at least 20%, preferably by more than 50% and extremely preferably by more than 70%. In particular, the fire protective component has an average particle size of 1-50 μ ^ ι, preferably 5-15 μιτι. Due to the small particle size, the flame retardant powder is well dispersed into the polymer powder.

The flame retardants contained in the powder of the invention exhibit ammonium polyphosphate as the main component. The phosphorus content of the ammonium polyphosphate is preferably 10-35% by weight, especially 15-32% by weight and extremely preferably 20-32% by weight. This flame retardant is preferably halogen-free. It may, however, show synergists, for example carcinogens, such as polyalcohols or pentaerythritol, and / or, for example, swelling (foaming) ingredients, such as melamine. In addition, sulfur may be included in the composition. This flame retardant may, when it is in the form of a powder, have a coating to mediate miscibility or to reduce the moisture sensitivity of the ammonium polyphosphate. Such coated flame retardants are, for example, available from Budenheim Iberica under the name Budit.

Commercially available examples of flame retardants that exhibit ammonium polyphosphate are generally Budit 3076 DCD or Budit 3076 DCD-2000 from Budenheim Iberica, or Exolit products from the AP series, for example Exolit AP 750 or Exolit AP 422 from Clariant.

The powder according to the invention can also have at least one excipient, at least one filler and / or at least one pigment. Such excipients may be, e.g., flow aids, e.g. pyrogenic silica or precipitated silicic acid. Pyrogenic silica (pyrogenic silicic acid) is offered, for example, under the product names Aerosil®, with various specifications, by Degussa AG. In particular, flow aids can be hydrophobic flow aids. Preferably, the powder according to the invention has less than 3% by weight, preferably 0.001-2% by weight and extremely preferably 0.05-1% by weight of such excipients based on the total of the ingredients, i.e. the sum of polymers and flame retardants. Fillers can be e.g. glass, metal particles, especially aluminum particles, or ceramic particles, such as e.g. solid or hollow glass spheres, steel spheres, aluminum spheres or metallic grit, or also colored pigments such as transition metal oxides.

Preferably, the filler particles exhibit smaller or almost as large medium particle size as the polymer particles. Medium grain size d₅₀ these fills9 or would preferably exceed the average grain size d₅₀polymers not more than 20%, especially not more than 15% and extremely preferably not more than 5%. Particle size is in particular limited by the permissible height of the structure or the thickness of the layer in each case, layers of the operating apparatus.

Preferably, the powder according to the invention has less than 70% by weight, especially 0.001-60% by weight, particularly preferably 0.05-50% by weight and extremely preferably 0.5-25% by weight of such fillers based on the total sum of ingredients, so that the volume fraction polymers in each case was more than 50%.

If the maximum limits specified for excipients and / or fillers are exceeded, depending on the filler or excipient used, the mechanical properties of molded products which have been produced with such powders may clearly deteriorate.

The preparation of the powder according to the invention is easily possible and is preferably carried out according to the method according to the invention for the production of the powder according to the invention, which process is distinguished in that at least one polymer is mixed with at least one flame retardant having ammonium polyphosphate. This mixing can take place dry in a loose composition. Preferably a polymeric powder, obtained e.g. by precipitation or milling, which can then be further fractionated, is mixed with a flame retardant that has ammonium polyphosphate. The advantage here may also be to supply the powdered flame retardant alone or the ready mixture with a flow aid, for example from the Aerosil range from Degussa, e.g. Aerosil R972 or R812. In another variant of the process, a flame retardant exhibiting ammonium polyphosphate can be spread in the polymer melt while mixing and the resulting mixture processed into powder by milling. The processing of flame retardants based on ammonium polyphosphate when mixing ingredients is described, for example, in Plastics Additives & Compounding, April 2002, Elsevier Advanced Technology, pages 28-33.

The fine mixing can, for example, be carried out by mixing the finely powdered flame retardant with dry dust in high speed mechanical mixers in the simplest method of carrying out the method according to the invention.

In the case of one of the first variants of the process according to the invention, this powder can already be a suitable polymer powder for the layer-forming rapid formation process to which fine particles of flame retardant are usually admixed. Preferably, these particles exhibit smaller to, at most, almost as high average grain size as polymer particles. Medium grain size d₅₀ flame retardant particles should preferably be lower than the average particle size d₅₀ polymeric powders by more than 20%, especially by more than 50% and extremely preferably by more than 70%. Particle size is particularly limited by the permissible height of the structure or the thickness of the layer in the device for rapid prototype creation.

It is also possible to mix traditional polymer powders with the powders according to the invention. Powders with an optimal combination of mechanical and anti-smoking properties can be produced in this way. The method of producing such mixtures can be taken from DE 34 41 708.

In a further variant of the process, the flame retardant is preferably mixed in the polymer melt while stirring and the resulting polymer containing the flame retardant is processed by milling (cold) and optional fractionation into a powder according to the invention. Usually, if the ingredients are mixed, granules are obtained, which are then processed into powder. This processing can take place e.g. by milling. Variants of the procedure in which the flame retardant is spread while stirring have the advantage over the method of pure mixing that homogeneous dispersion of the flame retardant powder is obtained.

In order to improve the flowability of the powder according to the invention, suitable flow support, such as pyrogenic alumina, pyrogenic silica or pyrogenic titanium dioxide, can be externally added to the precipitated or cold ground powder.

In order to improve the melting behavior during production of the molded article, a leveling agent may be added to the precipitated or cold milled powder, such as, for example, metallic soaps, preferably alkali monocarboxylic or beryllium salts, which are the base salts.

As flame retardants, the above-described products or commercially available products can be used, which can be purchased, for example, from Budehheim Iberica or Clariant under the trade names Exolit AP® or Budit®.

Metallic soaps are used in an amount of 0.01-30% by weight, preferably 0.5-15% by weight, based on the sum of the polyamides present in the powder. Preferably, sodium or calcium salts of alkanomonecarboxylic acids or dimeric acids on which the salts are based are used as metallic soaps. Examples of commercially available products are Licomont NaV or Licomont CaV from Clariant.

Metallic soap particles can be made into polyamide particles, but mixtures of fine metallic soap particles and polyamide particles may also be present.

In order to improve processability or to further modify the powder, inorganic pigments, especially colored pigments, such as e.g. transition metal oxides, stabilizers, e.g. phenols, especially sterically hindered phenols, flowability improvers and flow aid may be added to it. , such as e.g. pyrogenic silicas and filler particles. With respect to the total weight of the powdered ingredients, it is preferable to add enough powders to the powders to maintain the filler and / or excipient concentrations reported for the powder of the invention.

The subject of the present invention is also the use of the powder according to the invention for the production of molded articles in layers by means of a working selective binding process (a method of rapid prototype formation or a production method), in which the powders according to the invention which polymer and flame retardant containing ammonium polyphosphate are used preferably each time have a partial form.

In particular, the present invention relates to the use of a powder for the production of molded products by means of selective laser sintering comprising a flame retardant, a polyamide 12 precipitation powder which has a melting point of 185-189 ° C, a melting enthalpy of 112 ± 17 J / g and a pour point -145 ° C and the use of which is described in US 6,245,281.

The methods of laser sintering are sufficiently known and rely on the selective sintering of polymer particles, wherein the layers of polymer particles are briefly exposed to laser light, and so the polymer particles that have been exposed to laser light combine with each other. Three-dimensional objects are produced by subsequent sintering the layers of polymer particles. Details of the selective laser sintering method can be obtained e.g. from US 6,136,948 and WO 96/06881. The powder according to the invention, however, can also be used in other methods of rapid prototyping (Rapid-Prototyping) or rapid production (Rapid-Manufacturing) from the prior art, especially used in the methods described above. Thus, the powder according to the invention can be used in particular for the production of molded powdered products by the SLS method (selective laser sintering method) as described in US 6,136,948 or WO 96/06881, by the SIV method (method of selective inhibition of powder binding), which described in WO 01/38061, by three-dimensional printing as described in EP 0 431 924, or by a microwave method as described in DE 103 11 438. The descriptions cited, in particular the methods described therein, clearly belong to the content of the disclosure of the present description of the invention.

Due to the sensitivity of the flame retardant to air, careful handling should be recommended when handling the powder according to the invention. In particular, prolonged contact of the powder according to the invention with air or air humidity should be avoided. By the use of hydrophobic flow aids, this sensitivity of the powder according to the invention can be reduced, so that a reduction in the elastic modulus that is possibly caused by the decomposition products of ammonium polyphosphate can be avoided.

Molded articles according to the invention, produced by means of a three-dimensional object layered construction method in which the selective parts of the powder, especially the powder according to the invention, are bonded together, e.g. in the case of selective laser sintering, they are characterized in that they exhibit at least one flame retardant containing ammonium polyphosphate and at least one polymer or consist of at least one flame retardant containing ammonium polyphosphate and of at least one polymer. The molded articles according to the invention preferably have at least one polyamide which contains at least 8 carbon atoms per one carbonamide group. The molded articles according to the invention extremely advantageously exhibit at least one polyamide 612, polyamide 11 and / or polyamide 12 or copolyamides based on these polyamides, and at least one flame retardant exhibiting ammonium polyphosphate.

The flame retardant present in the molded article of the invention is based on ammonium polyphosphate. The molded article according to the invention primarily shows, with respect to the sum of the ingredients present in the molded article, 5-50% by weight of a flame retardant containing ammonium polyphosphate, preferably 10-40% by weight, particularly preferably 20-35% by weight and extremely preferably 23- 34% by weight. The maximum proportion of the protective agent containing ammonium polyphosphate is preferably 50% by weight based on the sum of the components present in the molded article. With respect to the sum of polymers present, the molded article exhibits 30-35% by weight of a flame retardant containing ammonium polyphosphate.

In addition to the polymer and flame retardant, these molded products may also contain fillers and / or auxiliaries and / or pigments, e.g. heat stabilizers, and / or oxidation stabilizers, e.g. sterically hindered phenol derivatives. Fillers can be e.g. glass and ceramic particles as well as metallics particles, e.g. iron balls, or suitable hollow balls. Preferably, the molded articles of the invention exhibit glass particles, particularly preferably glass spheres. The molded products according to the invention mainly exhibit less than 3% by weight, preferably 0.001-2% by weight and extremely preferably 0.05-1% by weight of such auxiliaries with respect to the sum of the components present. Equally preferably, the molded products of the invention have less than 75% by weight, preferably 0.001-70% by weight, particularly preferably 0.05-50% by weight and extremely preferably 0.5-25% by weight of such fillers with respect to the sum of the components present.

The following examples explain the powder composition of the invention and its use without limiting the invention to these examples.

The BET surface determination in the examples given below was carried out according to DIN 66 131. The bulk density was determined using apparatus according to DIN 53 466. The measurement values ​​of laser deflection were obtained in a device called Malvern Mastersizer S, version 2.18.

Example 1: Comparative example (not according to the invention) kg of unregulated, by hydrolytic polymerization of the polyamide PA 12 produced (prepared based on DE 35 10 691, example 1) with a relative dissolution viscosity n_rel. on the order of 1.61 (in acidified m-cresol) and with an end group content of 72 mmol / kg COOH or 68 mmol / kg NH₂ together with 0.3 kg of the agent called IRGANOX⁸ 1098 in 350 L of ethanol, treated with 2-butanone and 1% water content, was fed over a 5 hour period in a 0.8 m mixer³ (D = 90 cm, h = 170 cm) to 145 ° C and under stirring conditions (paw mixer, d = 42 cm, rotational speed 91 rpm) was left at this temperature for 1 hour. The jacket temperature is then reduced to 120 ° C and the internal temperature is brought to 120 ° C by means of a cooling rate of 45 K / h at the same agitator speed. From now on, the jacket temperature is kept at 2-3 ° K below the internal temperature at the same cooling rate. The internal temperature is brought to 117 ° C with an equal cooling rate and then kept unchanged for 60 minutes. The internal temperature is then brought to 111 ° C. with a cooling rate of 40 K / h. At this temperature, precipitation begins, which is recognizable by the development of heat. After 25 minutes the internal temperature drops, which indicates the end of precipitation. After cooling the suspension to a temperature of 75 ° C, the suspension is transferred to a rake dryer. From it, ethanol is distilled off on a mobile stirrer at 70 ° C at 400 hPa, and the residue is then dried for 3 hours at 20 hPa at 85 ° C.

BET: 6.9 mVg

Bulk density: 429 g / l

Laser deflection: d (10%): 42 gm, d (50%): 69 gm, d (90%): 91 gm. Example 2: Making a product called Budit 3076 DCD by mixing and then grinding kg of controlled, by hydrolytic polymerization of the polyamide PA 12 produced, Vestamid L1600 type from Degussa AG, together with 0.3 kg of the product called IRGANOX® 245 and 12 kg (30 parts) of the flame retardant (Budit 3076 DCD, from Budenheim Iberica) is extruded at 220 ° C in a twin-roll mixing machine (Bersttorf ZE25) and granulated in the form of a strand. This granulate is then ground to a grain size of 0-120 gm at low temperature (-40 ° C) in an impact mill. Then 40 g of Aerosil 200 (0.1 parts) are mixed in at 3 minutes at room temperature at 500 rpm.

Example 3: Making a product called Budit 3076 DCD-200 in a loose composition

Up to 1900 g (65 parts) of polyamide 12 powder, prepared according to example 1 of DE 29 06 647, with an average grain diameter of d₅₀ on the order of 56 μπι (laser deflection) and with a bulk density according to DIN 53 466 on the order of 459 g / l, 1023 g (35 parts) of the agent Budit 3076 DCD-2000 are admixed in the bulk composition method in 3 minutes at 700 rpm temperature 50 ° C using a Henschel FML10 / KM23 mixer. 1.5 g of Aerosil R 812 (0.05 parts) are then mixed at room temperature at 500 rpm for 3 minutes with stirring.

Further powders were produced under the same conditions that had 10, 20, 25, 30 and 35 parts of a flame retardant called Budit 3076 DCD-2000.

Example 4: Making a product called Budit 3076 DCD and metallic soap in an untermischen loose composition

Up to 1900 g (70 parts) of polyamide 12 powder, prepared according to example 1 of DE 29 06 647, with an average grain diameter of d₅₀ on the order of 56 μη (laser deflection) and with a bulk density according to DIN 53 466 on the order of 459 g / l, 814 g (30 parts) of the Budit 3076 DCD agent are admixed in the bulk composition method in 3 minutes at 700 rpm at 50 ° C using a Henschel FML10 / KM23 mixer. Then 54 g (2 parts) of the agent called Licomont NaV and 2 g Aerosil 200 (0.1 parts) are mixed at room temperature at 500 rpm for 3 minutes with stirring.

Example 5: Making a drug called Exolit AP 422 in a loose composition

Up to 1900 g (70 parts) of polyamide 12 powder, prepared according to example 1 of DE 29 06 647, with an average grain diameter of d₅₀ on the order of 56 μ] χι (laser deflection) and with a bulk density according to DIN 53 466 on the order of 459 g / l, 475 g (20 parts) of the agent called Exolit AP 422 is admixed in the bulk composition method in 3 minutes at 700 rpm temperature 50 ° C using a Henschel FML10 / KM23 mixer. 2.4 g of Aerosil 200 (0.1 parts) are then mixed at room temperature at 500 rpm for 3 minutes with stirring.

Further powders were produced under the same conditions which had 10, 20, 25, 30 and 35 parts of a flame retardant called Exolit AP 422.

Further processing and test

The powders of examples 1-4 were used in a laser sintering machine for the construction of bars for the fire protection test according to UL94V and multi-purpose bars according to ISO 3167. On these latter structural elements mechanical values ​​were determined using a tensile test according to EN ISO 527 (Table 1). UL rods were used for the vertical smoking test according to UL94V (Underwriters Laboratories Inc.). These rods have a given size of 3.2x10x80 mm. The production was always carried out in a laser sintering machine called EOSENT P360 from EOS GmbH.

Table 1: Test results of samples according to examples 1-3

<td>Examples</td><td>Thickness rod test [Mm]</td><td>Module EN / mm²</td><td>UL Whole time smoking [S]</td><td>UL Classification</td>

<td>The article formed from the material of example 1</td><td> 3,9</td><td> 1688</td><td> &gt;167</td><td>kE</td>

<td>The article formed from the material of example 2</td><td> 3,6</td><td> 1890</td><td> 19</td><td>VO</td>

<td>The article formed from the material of example 4, 30% Budit 3076 DCD-2000</td><td> 3,6</td><td> 1860</td><td> 11</td><td>VO</td>

<td>The article formed from the material of example 3, 30% Budit 3076 DCD-2000</td><td> 3,6</td><td> 1885</td><td> 10</td><td>VO</td>

<td>The article formed from the material of example 3, 35% Budit 3076 DCD-2000</td><td> 3,6</td><td> 2031</td><td> 9</td><td>VO</td>

<td>The product formed from the material of example 5, 30% Exolit AP 422</td><td> 3,7</td><td> 2313</td><td> 10</td><td>VO</td>

<td>The product formed from the material of Example 5, 20% Exolit AP 422</td><td> 3,7</td><td> 2207</td><td> 10</td><td>VO</td>

(kE: Classification in one of the V0-V2 stages was not possible. These rods are thicker than the set thickness, which should first be reduced to z-compensation (the laser beam reaches more than one layer thickness, because it also has to reach the layer boundary) , which in the case of this first layer, however, is a bit too much) and secondly it should be reduced to the easily swollen (foaming) action of some flame retardants.)

It should be clearly acknowledged that by adding a flame retardant based on ammonium polyphosphate to the polymer powder, molded products can be produced that exhibit clearly better UL classification. By addition of the flame retardant, an increase in the elastic modulus and tensile strength is also achieved, however the elongation at break is also reduced.

Degussa GmbH

Deputy:

OK II-12 / P21737PL00

EP 1 648 958 B1