AU2012200781A1 - Core-shell polyamide powder - Google Patents

Abstract

The invention relates to a method for preparing a powdered polymer selected from a polyamide, a copolyamide or a 5 copolyesteramide by anionic polymerisation in a solvent solution, characterised in that the polymerisation of the monomer(s) generating said polymer is made in the presence of a catalyst, an activator, at least one amide, one of which is always a N, N' alkylene bis amide, and an inorganic or organic feedstock, the 10 amount of N, N'-alkylene bis aide added in the medium being determined based on the specific surface area desired for the powder particles, said powder particles having an essentially constant diameter or one depending on the desired mean diameter of the powder particles, said powder particles having an 15 essentially constant specific surface area.

Description

Secion 29 Regulaion 32(2) AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Application Number: Lodged: Invention Title: Core-shell polyamide powder The following statement is a full description of this invention, including the best method of performing it known to us: P111AHAU/0710 METHOD FOR PREPARING POLYAMIDE POWDER BY ANIONIC POLYMERISATION Porous powder particles of polyamide, copolyamide or 5 copolyesteramide are spherical or near-spherical particles with an average diameter of less than 100 pm, preferably less than 50 pm. These particles, which have a controlled Apparent Specific Surface Area (ASSA), constitute a major asset in applications such as the 10 following: composite materials, transfer papers, the coating of substrates, especially metallic substrates (coil coating), solid or liquid paint and ink compositions, the agglomeration of polyamide powders by compression with or without metal particles, or by 15 sintering or melting induced by radiation such as, for example, a laser beam (laser sintering), infrared radiation or UV radiation (UV curing), and cosmetic and/or pharmaceutical formulations. 20 The industrial production of porous polyamide particles, especially spheroidal particles, with a narrow particle-size distribution is known by anionic polymerization of lactam(s) in suspension (FR1213993, FR1602751) or in solution (DE1183680) in an organic 25 liquid. The processes described in these patents allow direct production of polyamide particles which separate by themselves from the liquid medium at the rate at which they are formed. Patent EP0192515 describes the anionic polymerization of a lactam in a stirred reactor 30 in a solvent in the presence of a catalyst, an activator, an N,N'-alkylenebisamide, and, optionally, an organic or inorganic filler. The size of the particles may be compensated by acting on various parameters of the process: the reaction temperature, 35 the amount of catalyst, the rate of injection of the activator, the stirring speed, the filler content.

- 2 TABLE A Average diameter ASSA [mp ] [m 2 /g] Orgasol@2002 UD 5 9 Orgasol@2002 EXD 10 4 Orgasol@2002 D 20 1.5 Orgasol@2002 ES3 30 The polyamide powder particles on the market show that, 5 for an increasing average diameter, the ASSA reduces, as shown in table A above. However, in order to respond to the requirement of the market, it is important to produce polyamide, 10 copolyamide or copolyesteramide powder particles which, for a given average diameter, fall within the widest possible range of apparent specific surface area (ASSA), with ASSAs which are preferably as high as possible, or which, for a given ASSA, fall within the 15 widest possible range of average diameter, with average diameters which are preferably as low as possible. The applicant has now found a solution to this technical problem, and demonstrates below that, to 20 obtain polyamide, copolyamide or copolyesteramide particles with a narrow particle-size distribution, with an average diameter of less than 100 pm, preferably less than 50 pm, advantageously less than 30 pim, even more advantageously less than 20 yrm, and 25 with an ASSA of less than 50 m2/g, advantageously less than 40 m2/g, even more advantageously less than 30 m2/g, the anionic polymerization in solution in a solvent of the constituent monomer or monomers of said polymer is carried out in the presence of a catalyst, 30 an activator, at least one amide, of which one is always an N,N'-alkylenebisamide, and an organic or inorganic filler, the amount of N,N'-alkylenebisamide -3 added to the medium being determined as a function of the Apparent Specific Surface Area (ASSA) and/or of the average diameter of the particles it is desired to obtain. This is termed anionic polymerization by 5 seeding with an organic or inorganic filler. This concept of seeding is to be differentiated from the concept of coating which is addressed in the applicant's patent EP196972, and which has nothing to do with the present invention. 10 Seeding is referred to when the thickness of the polymer layer of the eventual seeded particle is greater than the radius of the filler whose density is not more than 4.5 cm3/g. Conversely, coating is 15 referred to when the thickness of the polymer layer of the eventual coated particle is less than the radius of the filler whose density is not more than 4.5 cm3/g. Fig. 1 is a photograph of the powder of the invention 20 obtained in Ex. 1, and Fig. 2 is a photograph of the powder of the invention obtained in Ex. 2. The invention provides a process for preparing powder of polymer selected from a polyamide, a copolyamide or 25 a copolyesteramide by anionic polymerization in solution in a solvent, characterized in that said polymerization of the constituent monomer or monomers of said polymer is carried out in the presence: * of a catalyst, 30 e of an activator, * of at least one amide selected from N,N' -alkylenebisamides, and * of an organic or inorganic filler with a maximum density of 4.5 cm3/g, 35 the amount of amide added to the reaction medium being determined as a function of the Apparent Specific Surface Area (ASSA) it is desired to obtain for powder particles, said powder particles having a substantially constant diameter. In one embodiment the process for preparing powder of 5 polymer selected from a polyamide, a copolyamide or a copolyesteramide by anionic polymerization in solution in a solvent is characterized in that said polymerization of the constituent monomer or monomers of said polymer is carried out in the presence: 10 e of a catalyst, e of an activator, e of at least one amide selected from N,N' -alkylenebisamides, and * of an organic or inorganic filler with a 15 maximum density of 4.5 cm3/g, the amount of amide added to the reaction medium being determined as a function of the average diameter it is desired to obtain for powder particles, said powder particles having a substantially constant Apparent 20 Specific Surface Area (ASSA). In one embodiment the process is characterized in that, when the amount of aide goes up, the ASSA goes up. 25 in one embodiment the process is characterized in that, when the amount of amide goes up, the average diameter goes down. In one embodiment the process is characterized in that 30 the constituent monomer or monomers of the polymer is or are selected from lactams such as lauryllactam, caprolactam, enantholactam, capryllactam or mixtures thereof, preferably, lauryllactam alone, caprolactam alone or the mixture thereof. 35 In one embodiment the process is characterized in that the constituent monomers of the polymer are a mixture comprising in molar %, the total being to 100%: - 5 " from 1% to 98% of a lactam selected from lauryllactam, caprolactam, enantholactam, and capryllactam; " from 1% to 98% of a lactam other than the 5 first, selected from lauryllactam, caprolactam, enantholactam, and capryllactam; " from 1% to 98% of a lactone selected from caprolactone, valerolactone, and butyrolactone; advantageously 30-46% of caprolactam, 30-46% of 10 lauryllactam, and 8-40% of caprolactone. In one embodiment the process is characterized in that the catalyst is selected from sodium hydride, potassium hydride, sodium, and sodium methoxide and ethoxide. 15 In one embodiment the process is characterized in that the activator is selected from lactam N-carboxy anilides, (mono) isocyanates, polyisocyanates, carbodi imides, cyanamides, acyllactams and acylcarbamates, 20 triazines, ureas, N-substituted imides, esters, and phosphorus trichloride. t activator is selected from lactam N-carboxyanilides, (mono) isocyanates, polyiso cyanates, carbodiimides, cyanamides, acyllactams and acylcarbamates, triazines, ureas, N-substituted imides, 25 esters, and phosphorus trichloride. In one embodiment the process is characterized in that the N,NT-alkylenebisamide is selected from N,N' -ethylenebisstearamide (EBS) and N, N -ethylene 30 bisoleamide (EBO). In one embodiment the process is characterized in that the inorganic filler is selected from silicas, aluminosilicates, aluminum oxides or alumina, titanium 35 dioxides, and BN. Tn one embodiment the process is characterized in that the organic filler is selected from homo- or -6 copolyamide polyamide powders, preferably powders of PA12, PAll, PA6, PA6-12, PA 6,12, PA 6,6, PAS, PA4, of polystyrenes, of polyurethanes, of poly(methyl) methacrylates (PMMA), of polyacrylates, of polyesters, 5 of silicones, of polyethylenes, and of polytetra fluoroethylene . In one embodiment the process is characterized in that the distribution of the particles is narrower than that 10 of the particles obtained by the process defined above. In one embodiment the process is characterized in that the powder particles obtained have an average diameter < 30 microns, advantageously < 20 microns. 15 In one embodiment the process is characterized in that the ASSA < 40 m 2 /g, advantageously < 30 m2 g The invention also provides polymer powder particles 20 selected from a polyamide, a copolyamide or a copolyesteramide obtained by the process defined above. In one embodiment the particles are characterized in that the organic filler is an Orgasol®. 25 The invention further provides a composition of above particles, characterized in that it further comprises at least one compound selected from carbon nanotubes, metal particles, pigments, dyes, antioxidants, anti-UV 30 agents, plasticizers, and carbon black. The invention provides, moreover, for the use of the powder particles obtained by the process described above, of the particles described above or of the 35 composition defined above to manufacture composite materials, transfer papers, substrate coatings, particularly on metallic substrates (coil coating), solid or liquid paint or ink compositions, cosmetic - 7 compositions and/or pharmaceutical compositions, in one embodiment, to manufacture articles by agglomeration of said powder, alone or in composition, by compression or by sintering or melting induced by radiation such as a 5 laser beam (laser sintering) , infrared radiation or UV radiation (UV curing). A substantially constant diameter means that, for a given process, the average diameter of the particles 10 obtained from one batch to the next may vary within a diameter range of greater than or less than 20% in relation to the average of the average diameters from the different batches. For example, for batches for which the average of the average diameters is 10 pm, 15 the range of variation is between 8 and 12 pm. A substantially constant ASSA means that, for a given process, the average ASSA of the particles obtained from one batch to the next may vary within an ASSA 20 range of greater than or less than 25% in relation to the average of the average ASSAs from the different batches. For example, for batches for which the average of the ASSAs is 4 m2/g, the range of variation is between 3 and 5 m2/g. 25 THE POLYMERIZABLE MONOMER OR MONOMERS The polymerizable monomer or monomers used in the invention is or are selected from lactams such as, for example, lauryllactam, caprolactam, enantholactam, 30 capryllactam or mixtures thereof . Preference is given to using lauryllactam alone, caprolactam alone, or the mixture thereof. It is also possible to consider the copolymerization of 35 two or more lactams with a lactone, leading to a copolyesteramide, as described in patent EP1172396. In this case the mixture copolymerized is a mixture comprising in molar %, the total being to 100%: - 8 from 1% to 98% of a lactam selected from lauryllactam, caprolactam, enantholactam, and capryl lactam; " from 1% to 98% of a lactam other than the 5 first, selected from lauryllactam, caprolactam, enantholactam, and capryllactam; " from 1% to 98% of a lactone selected from caprolactone, valerolactone, and butyrolactone. 10 In the case of a copolyesteramide it is advantageous to use caprolactam, lauryllactam, and caprolactone in the following respective proportions (molar %): 30-46%, 30-46%, and 8-40% (the total being to 100%) . 15 Preferably the process is applied to lactams and to mixtures thereof rather than to mixtures of two or more lactams and a lactone. THE OTHER INGREDIENTS OF THE POLYMERIZATION 20 An anionic polymerization which is conducted in order to obtain polyamide, copolyamide or copolyesteramide particles is performed in a solvent. 0 The solvent The solvent used dissolves the monomer or monomers but 25 not the particles of polymer which are formed during the polymerization. Examples of solvent are given in patent EP192515. Advantageously the solvent is a paraffinic hydrocarbon fraction with a boiling range at atmospheric pressure of between 120 and 170 C, 30 preferably between 140 and 170 0 C. The solvent may be supersaturated with monomer(s) at the initiation temperature, in other words at the temperature at which the polymerization begins. There 35 are various means of supersaturating the solvent with monomer(s) . One of these means may involve saturating the solvent with monomer(s) at a temperature greater than the initiation temperature, then lowering the - 9 temperature to the initiation temperature. Another means may involve substantially saturating the solvent with monomer(s) at the initiation temperature and then adding, still at the same temperature, a primary amide 5 containing preferably 12 to 22 carbon atoms, such as, for example, oleamide, N-stearamide, erucamide, isostearamide, or else an N,N'-alkylenebisamide, examples of which are given later on. 10 It is also possible to conduct the polymerization in a solvent which is not supersaturated with monomer(s) . In this case the reaction medium contains the monomer or monomers in solution in the solvent at a concentration distant from supersaturation at the initiation 15 temperature. e The catalyst A catalyst selected from the catalysts customary for the anionic polymerization of lactams is used. This is a base which is sufficiently strong to give a lactamate 20 after reaction with the lactam or mixture of lactams. A combination of two or more catalysts may be contemplated. Nonlimiting examples include sodium hydride, potassium hydride, sodium, and sodium methoxide and/or ethoxide. The amount of catalyst(s) 25 introduced may in general vary between 0.5 and 3 moles per 100 moles of monomer(s) * The activator An activator is added as well, its role being to stimulate and/or accelerate the polymerization. The 30 activator is selected from lactam N-carboxyanilides, (mono) isocyanates, polyisocyanates, carbodiimides, cyanamides, acyllactams and acylcarbamates, triazines, ureas, N-substituted imides, esters, and phosphorus trichloride. It may optionally also be a mixture of two 35 or more activators. The activator may also optionally be formed in situ, for example, by reaction of an alkyl isocyanate with the lactam to give an acyllactam.

- 10 The molar catalyst/activator ratio is between 0.2 and 2, preferably between 0.8 and 1.2. * The amide Also added is at least one amide, one of which is 5 always an N,N'-alkylenebisamide, as indicated in EP192515. The amount of N,N'-alkylenebisamide(s) introduced is generally of the order of 0.001 to 4 moles, preferably of 0.075 to 2 moles, per 100 moles of monomer(s) . The particularly recommended 10 N,N'4--alkylenebisamides include the N,N'-alkylenebis amides of fatty acids, and more particularly: > N,N'-Ethylenebisstearamide of formula

C

17

H

3 5 -C (=O) -NH-CH 2 CH:rNH-C (=0) -C 7 Hr 35 , abbreviated EBS. 15 > N,N'-Ethylenebisoleamide of formula C17H33-C (=0) -NH-CH2CH2-NH-C (=0) -C17H33, abbreviated EBO. N,N' -Alkylenebispalmitamide, -gadoleamide, -cetoleamide, and -erucamide. 20 Preference is given to using EBS and/or EBO. It is also possible to add a primary aide containing preferably 12 to 22 carbon atoms. It may be selected from the following: oleamide, N-stearamide, isostear amide, and erucamide. 25 * The inorganic filler The density of the inorganic filler is not more than 4.5 cm3/g and it is selected from silicas, aluminosilicates, aluminum oxides or alumina, titanium dioxides, and BN (for example, Tres BN@ from Saint 30 Gobain). It may also be a mixture of these inorganic fillers. In the case of a mixture of inorganic fillers mentioned above, there may be, by way of example, a mixture of 35 different silicas, a mixture of a silica and an alumina, or else a mixture of a silica and titanium dioxide.

- 11 * The organic filler The organic filler has a density of not more than 4.5 cm3/g and is a powder of homo- or copolyamide polyamide, preferably of PA12, PAll, PA6, PA6/12, S PA 6,12, PA 6,6, PA8, PA4 (for example, Orgasol@ powders from Arkema, Vestosint@ powders from Degussa, etc.), of polystyrenes, of polyurethanes, of poly(methyl) methacrylates (PMMA), of polyesters, of silicones, of polyethylenes or of polytetra 10 fluoroethylene. The amount of organic or inorganic fillers and the diameter of said fillers make it possible to influence in the desired direction (small particles or- large particles) the size of the eventual particles obtained 15 at the end of the polymerization. * The other fillers or additives It is also possible to add to the reaction medium any type of fillers (pigments, dyes, carbon black, carbon nanotubes, etc.) or additives (antioxidants, anti-UV 20 agents, plasticizers, etc.) with the proviso that all of these compounds are thoroughly dry and inert with respect to the reaction medium. THE POLYMERIZATION 25 The anionic polymerization is performed continuously or else, preferably, discontinuously (batchwise) . The discontinuous procedure involves introducing the solvent and then, simultaneously or successively, the monomer or monomers, optionally an N,N'-alkylenebis 30 amide, the filler, the catalyst, and the activator. It is advisable first to introduce the solvent and the monomer or monomers and then to remove the water, with the aid for example of azeotropic distillation, and then to add the catalyst when the medium contains as 35 few molecules of water as possible. The filler may be introduced, for example, after the introduction of the monomer or monomers. It may be advantageous, in order to prevent solidification or loss of control of the - 12 polymerization, to introduce the activator not in one go at a time t, but either in one go over a shorter or longer interval at a constant rate or with a rate gradient, or in steps, with different rates for each 5 step. Operation takes place at atmospheric pressure or else under a slightly higher pressure (partial pressure of the hot solvent) and at a temperature between 200C and 10 the boiling temperature of the solvent. The temperature of initiation and of polymerization of the lactams is in general between 70 and 1500C, preferably between 80 and 1300C. 15 The [organic or inorganic filler/monomer or monomers introduced into the reaction medium] weight ratio, expressed in %, is between 0.001% and 65%, preferably between 0.005% and 45%, more preferably between 0.01% and 30%, and advantageously between 0.05% and 20%. 20 The powders according to the invention may be used in the context of the process of producing articles by melting induced by a laser beam (laser sintering) , IR radiation or UV radiation. The technique of laser 25 sintering is described in the applicant's patent application EP1571173. THE EXAMPLES: We are now going to give examples of the invention (see 30 tables 1 and 2 below). * Measurement of the particle size of the powders obtained The powders obtained in the inventive and comparative examples below are analyzed using a Coulter LS230 35 granulometer. This gives the particle-size distribution of the powders, from which it is possible to ascertain: > The average diameter.

- 13 > The breadth of the distribution or the standard deviation of the distribution. The particle-size distribution of the powders according 5 to the invention is determined by the customary methods, using a Coulter LS230 granulometer from Beckman-Coulter. From the particle-size distribution it is possible to ascertain the volume-average diameter with the logarithmic calculation mode, version 2.11a. 10 of the software, and also the standard deviation, which measures the narrowness of the distribution or the breadth of the distribution around the average diameter. One of the advantages of the process described here is to allow a narrow distribution (low 15 standard deviation) to be obtained in relation to the average diameter. This standard deviation is calculated using the logarithmic statistical calculation mode, version 2.11a. of the software. 20 * Measurement of the apparent specific surface area (ASSA) The apparent specific surface area of the particles was measured by the BET method (ten points) with the SA3100 from Beckmann-Coulter. The BET (Brunauer-Fmet-Teller) 25 method is a method which is well known to the skilled worker. It is described in particular in Journal of the American Chemical Society, vol. 60, page 309, February 1938, and corresponds to international standard ISO 5794/1 (annex D) . The specific surface area measured by 30 the BET method corresponds to the total specific surface area - that is, it includes the surface formed by the pores. The BET technique involves absorbing a monomolecular layer of gas molecules on the surface. The gas used is nitrogen. 35 EXAMPLES SEEDED WITH INORGANIC FILLER (TABLE 1 BELOW): Example 1: - 14 The reactor, maintained under nitrogen, is charged with 2210 ml of solvent and then, in succession, with 719 g of dry lauryllactam, 21.5 g of EBS, 0.45 g of N-stearamide, and 13.8 g of AEROSIL@ R972 finely 5 divided silica. After commencement of stirring at 350 rpm, the mixture is heated gradually to 1101C and then 265 ml of solvent are distilled off under vacuum in order to entrain, azeotropically, traces of water that might be present. 10 Following a return to atmospheric pressure, the anionic catalyst and 1.44 g of sodium hydride of 60% purity in oil are introduced rapidly under nitrogen, and the stirring is increased to 650 rpm, under nitrogen at 15 1100C for 30 minutes. Then the temperature is taken to 95OC and, using a small metering pump, the activator selected, namely stearyl isocyanate (41.3 g made up to 323.2 g with the 20 solvent), is injected continuously into the reaction medium in accordance with the following program: > 21.6 g/h of isocyanate solution for 300 minutes; > 77.6 g/h of isocyanate solution for 25 150 minutes. In parallel the temperature is maintained at 95 0 C for the first 300 minutes and then is raised to 1200C over 30 minutes and maintained at 120 0 C for a further 30 2 hours after the end of introduction of the isocyanate. The polymerization is then at an end and the reactor is almost clean. 35 After cooling to 80 0 C, decanting, and drying, the particle size is between 1 and 20 pm, the average - 15 diameter of the particles is 6 pm without agglomerate, and the ASSA is 20.7 m 2 /g. 5 Example 2; Example 1 is reproduced but using 14.5 g of EBS. When the polymerization is at an end, the reactor is almost clean. The particle size is between 1 and 20 pm, the average diameter of the particles is 6.3 pm without 10 agglomerate, and the ASSA is 7.1 m2/g Comparing example 1 and example 2, it is observed that the reduction in the amount of EBS results in a large drop in the ASSA for a comparable particle size. 15 Example 3: The reactor, maintained under nitrogen, is charged with 2800 ml of solvent and then, in succession, with 899 g of dry lauryllactam, 27.7 g of EBS, 0.45 g of N-stearamide, and 3.6 g of AEROSIL® R972 finely divided 20 silica. After commencement of stirring at 350 rpm, the mixture is heated gradually to 110 0 C and then 290 ml of solvent are distilled off under vacuum in order to entrain, azeotropically, traces of water that might be present. 25 Following a return to atmospheric pressure, the anionic catalyst and 1.44 g of sodium hydride of 60% purity in oil are introduced rapidly under nitrogen, and the stirring is increased to 720 rpm, under nitrogen at 30 1100C for 30 minutes. Then the temperature is taken to 99.7 C and, using a small metering pump, the activator selected, namely stearyl isocyanate (55.7 g made up to 237.7 g with the 35 solvent), is injected continuously into the reaction medium in accordance with the following program: > 14.4 g/h of isocyanate solution for 300 minutes; - 16 > % 52.1 g/h of isocyanate solution for 175 minutes. In parallel the temperature is maintained at 99.7'C for 5 the first 300 minutes and then is raised to 120C over 30 minutes and maintained at 120 0 C for a further 1 hour after the end of introduction of the isocyanate. The polymerization is then at an end and the reactor is 10 almost clean. After cooling to 80 0 C, decanting, and drying, the particle size is between 2 and 25 pun, the average diameter of the particles is 10.0 pm, and the ASSA is 12.2 m 2 /g without agglomerate. Example 4: 15 The conditions used are the same as those for example 3, but without addition of N-stearamide. The polyamide 12 powder obtained has the following characteristics: Particle size between 2 and 25 pm with the average 20 diameter of the particles being 10.4 pm, and an ASSA of 7.7 m 2 /g without agglomerates; and the reactor is almost clean. Example 5: The reactor, maintained under nitrogen, is charged with 25 2800 ml of solvent and then, in succession, with 323 g of caprolactam, 575 g of dry lauryllactam, 30.9 g of EBS, and 10.8 g of finely divided silica. After commencement of stirring at 300 rpm, the mixture is heated gradually to l100C and then 290 ml of solvent 30 are distilled off under vacuum in order to entrain, azeotropically, traces of water that might be present. Following a return to atmospheric pressure, the anionic catalyst and 9 g of sodium hydride of 60% purity in oil 35 are introduced rapidly under nitrogen, and the stirring is increased to 720 rpm, under nitrogen at 110 0 C for 30 minutes.

- 17 Then the temperature is taken to 810C and, using a small metering pump, the activator selected, namely stearyl isocyanate (32.9 g made up to 323.9 g with the solvent), is injected continuously into the reaction 5 medium in accordance with the following program: > 53.9 g/h of isocyanate solution for 300 minutes, In parallel the temperature is maintained at 811C for 10 the first 300 minutes and then is raised to 110 0 C over 60 minutes and maintained at 1100C for a further 3 hours after the end off introduction of the isocyanate. The polymerization is then at an end and the reactor is almost clean. After cooling to 800C, 15 decanting, and drying, the particle size is between 2 and 25 pm, the average diameter of the particles is 11.7 pm, and the ASSA is 28.8 m 2 /g without agglomerate. Example 6: Example 5 is reproduced but using 7.2 g of EBS. When 20 the polymerization is at an end, the reactor is almost clean. The particle size is between 2 and 25 pm, the average diameter of the particles is 13.7 pm, and the ASSA is 15.9 m 2 /g without agglomerate. 25 Comparing example 5 and example 6, it is observed that the reduction in the amount of EBS results in a large drop in the ASSA for a slight increase in the average diameter. 30 EXAMPLES SEEDED WITH ORGANIC FILLERS (TABLE 2 BELOW): Example 7: The reactor, maintained under nitrogen, is charged with 2800 ml of solvent and then, in succession, with 108 g of caprolactam, 679 g of dry lauryllactam, 14.4 g of 35 EBS, and 112 g of finely divided ORGASOL@ 2001 UD NATl. After commencement of stirring at 300 rpm, the mixture is heated gradually to 110 0 C and then 290 ml of solvent - 18 are distilled off under vacuum in order to entrain, azeotropically, traces of water that might be present. Following a return to atmospheric pressure, the anionic 5 catalyst and 7.2 g of sodium hydride of 60% purity in oil are introduced rapidly under nitrogen, and the stirring is increased to 720 rpm, under nitrogen at 1100C for 30 minutes. 10 Then the temperature is taken to 96 0 C and, using a small metering pump, the activator selected, namely stearyl isocyanate (32.9 g made up to 314 g with the solvent), is injected continuously into the reaction medium in accordance with the following program: 15 > 10 g/h of isocyanate solution for 300 minutes; > 88 g/h of isocyanate solution for 180 minutes. In parallel the temperature is maintained at 96'C for the first 360 minutes and then is raised to 110 0 C over 20 60 minutes and maintained at 1100C for a further 2 hours after the end of introduction of the isocyanate. The polymerization is then at an end and the reactor is 25 almost clean. After cooling to 80 0 C, decanting, and drying, the particle size is between 2 and 20 pm, the average diameter of ~the particles is 11.8 pm, and the ASSA is 9.3 m 2 /g without agglomerate. Example 8: 30 Example 7 is reproduced but using 24.7 g of EBS. When the polymerization is at an end, the reactor is almost clean. The particle size is between 1 and 20 pim, the average diameter of the particles is 11.4 pm, without agglomerates, and the ASSA is 13.2 m 2 /g. 35 Example 9: Example 7 is reproduced but using 30.9 g of EBS. When the polymerization is at an end, the reactor is almost clean. The particle size is between 1 and 20 pm, the 19 average diameter of the particles is 11.4 pm, without agglomerate, and the ASSA is 15 m 2 /g. Comparing examples 7-9, it is observed that the increase in the 5 amount of EBS results in a large increase in the ASSA for a particle size or an average diameter which is virtually the same or substantially constant. TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex.4 Ex. 5 Ex. 6 Lactam 6 323 323 Lactam 12 719 719 899 899 575 575 EBS 21.5 14.5 27.7 27.7 30.9 7.2 N-Stearamide 0.45 0.45 0.45 Silica 13.8 13.8 3.6 3.6 10.8 10.8 Stearyl 41.3 41.3 55.7 55.7 32.9 32.9 isocyanate NaH 1.44 1.44 1.44 1.44 9 9 Average 6 6.3 10 10.4 11.7 13.7 diameter (Pm) ASSA (m 2 /g) 20.7 7.1 12.2 7.7 28.8 15.9 10 TABLE 2 Ex. 7 Ex. 8 Ex.9 Lactam 6 (g) 108 108 108 Lactam 12 (g) 679 679 679 EBS (g) 14.4 24.7 30.9 Organic filler (g) 112 112 112 EBS/lactam 54.65 31.86 25.47 Stearyl isocyanate 32.9 32.9 32.9 NaH 7.2 7.2 7.2 Average diameter (ym) 11.8 11.4 11.4 ASSA (m 2 /g) 9.3 13.2 15 20 Comprises/comprising and grammatical variations thereof when used in this specification are to be taken to specify the presence of stated features, integers, steps or components or groups thereof, 5 but do not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

Claims (7)

1. A process for preparing powder of polymer selected from a polyamide, a copolyamide or a copolyesteramide by anionic polymerization in solution in a solvent, characterized in that 5 said polymerization of the constituent monomer or monomers of said polymer is carried out in the presence: * of a catalyst, " of an activator, e of at least one amide selected from 10 N,N'-alkylenebisamides added in an amount of 0.001 to 4 moles per 100 moles of monomer, and " of an organic filler with a maximum density of

4.5 cm3/g, selected from homo- or copolyamide polyamide powders, preferably powders of PA12, PA11, 15 PA6, PA6-12, PA 6,12, PA 6,6, PAS, PA4, of polystyrenes, of polyurethanes, of poly(methyl) methacrylates (PMMA), of polyacrylates, of polyesters, of silicones, of polyethylenes, and of polytetra fluoroethylene, 20 said powder particles having a substantially constant diameter, wherein the average diameter < 30 microns, advantageously < 20 microns and having an ASSA < 40 m2/g, advantageously < 30 m2/g and further characterized in that, when 25 the amount of amide is increased, the ASSA increases. 2. The process of claim 1, characterized in that the constituent monomer or monomers of the polymer is or are selected from lactams such as lauryllactam, caprolactam, enantholactam, 30 capryllactam or mixtures thereof, preferably, lauryllactam alone, caprolactam alone or the mixture thereof. 3. The process of claim I or claim 2, characterized in that the constituent monomers of the polymer are a mixture comprising in molar %, the total being to 100%: 22 " from 1% to 98% of a lactam selected from lauryllactam, caprolactam, enantholactam, and capryllactam; " from 1% to 98% of a lactam other than the first, selected from lauryllactam, caprolactam, enantholactam, and 5 capryllactam; M from 1% to 98% of a lactone selected from caprolactone, valerolactone, and butyrolactone; advantageously 30-46% of caprolactam, 30-46% of lauryllactam, and 8-40% of caprolactone. 10 4. The process of any one of the preceding claims, characterized in that the catalyst is selected from sodium hydride, potassium hydride, sodium, and sodium methoxide and ethoxide.

5. The process of any one of the preceding claims, 15 characterized in that the activator is selected from lactam N carboxyanilides, (mono)isocyanates, polyisocyanates, carbodiimides, cyanamides, acyllactams and acylcarbamates, triazines, ureas, N-substituted imides, esters, and phosphorus trichloride. 20 6. The process of any one of the preceding claims, characterized in that the N,N'-alkylenebisamide is selected from N,N'-ethylenebisstearamide (EBS) and N,N'-ethylenebisoleamide (EBO).

7. Polymer powder particles selected from a polyamide, a 25 copolyamide or a copolyesteramide obtained as claimed in any one of claims 1 to 6.

8. A composition of particles of claim 7, characterized in that it further comprises at least one compound selected from carbon nanotubes, metal particles, pigments, dyes, antioxidants, anti-UV 30 agents, plasticizers, and carbon black. 23

9. The use of the powder particles obtained by the process of any one of claims 1 to 6, of the particles of claim 7 or of the composition of claim 8 to manufacture composite materials, transfer papers, substrate coatings, particularly on metallic 5 substrates (coil coating), solid or liquid paint or ink compositions, cosmetic compositions and/or pharmaceutical compositions.

10. The use of the powder particles obtained by the process of any one of claims I to 6, of the particles of claim 7 or of the 10 composition of claim 8 to manufacture articles by agglomeration of said powder, alone or in composition, by compression or by sintering or melting induced by radiation such as a laser beam (laser sintering), infrared radiation or UV radiation (UV curing). 15 11. A process for preparing powder of polymer substantially as hereinbefore described with reference to the examples. ARKEMA FRANCE 20 WATERMARK PATENT & TRADE MARK ATTORNEYS 25