DE1920777A1 - Method and device for the production of thermoplastic powders - Google Patents

Description

Badische Anilin- & Soda-Fabrik AG

Our reference: OZ 26 145 Ks / Be 6700 Ludwigshafen, Pl _{0 4.1969}

Method and device for the production of thermoplastic powders

The invention relates to a method and a device for Manufacture of thermoplastic powders by atomizing thermoplastics in a molten state.

There are basically three known processes for producing thermoplastic powders: precipitation, grinding and atomization. Precipitation is only possible for thermoplastics that have good solubility in common Solvents and can be obtained quickly and quantitatively in powder form by suitable precipitants permit. This method can advantageously be used with thermoplastics with polar structural components. A serious disadvantage of this process is that there are no powdery thermoplastics, which contain pigments or fillers in a homogeneous distribution, can be produced. In the case of thermoplastics with predominantly non-polar As a pulverization process, grinding remains structure or atomization.

By grinding 1, a number of thermoplastics are made into powder crush. However, this method has a number of disadvantages: As a result of the plastic behavior, the mills plastics have a high energy requirement. The heating during the grinding process can soften the Plastics come in, so cooling may be necessary to keep the products brittle. Furthermore, the Grinding generally small fines in the powder. It also indicates a decrease in the viscosity of milled melts Thermoplastic powders on a degradation of the plastic, which is associated with a deterioration in quality. The mills usually have low capacities, so that they are not very suitable for the production of large quantities of powder.

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Purely the production of thermoplastic powders by atomization

several methods are known.

According to that described in British Patent Specification 609,560 In the process, molten polyethylene is pressed through a nozzle and crushed with the aid of a stream of gas to make it powdery To obtain products, it is necessary to add substances to the polyethylene that reduce its viscosity. This will be but the mechanical properties of the polyethylene deteriorate. In addition, the powdered polyethylene is included this process, especially if the polyethylene does not contain any viscosity-reducing agents Substances are added, along with thread-like polyethylene.

It is also known from US Pat. No. 2,831,845, high pressure polyethylene To pulverize immediately after manufacture by removing the exiting from the reactor under high pressure Mixture of ethylene and molten polyethylene relaxes in a pipe and it is made ring-shaped by spraying water arranged nozzles. In this process, however, large losses of ethylene occur and the product has to be from separated from the water and dried.

In addition, a method for producing thermoplastic powders is known from German patent application P 14 54 760.5, in which molten plastics are pressed out of nozzle-shaped openings in the form of strands and the strands are inflated of a gas flow in an approximately perpendicular direction to the exit direction the strands are crushed. A disadvantage of this method is the general susceptibility to failure of the atomizing device, because the product holes easily clog and a back pressure of the product into the gas nozzle is observed, so that the system cannot be switched off and started up again several times. Before each new commissioning, the Removed and cleaned. Also, with the help of this process no products can be atomized, the solids contained in homogeneous distribution.

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As these examples show, are the well known sputtering methods not free from drawbacks. Their specific energy consumption is either uneconomically high in some cases, others are prone to failure and unsuitable for large-scale production or they result in a relatively coarse powder.

The object was therefore to show a method and a device with which it is possible in a technically simple manner atomizing thermoplastics into powders.

It has been found that this object is achieved if thermoplastics with temperatures between the melting point and the highest temperature permissible without chemical change in the product, with pressures between 5 and 300 atu and a muzzle velocity of 0.2 to 4 ni / sec in one Conically tapered! Annular flow from 5 to 40 ° cone angle and 0 to 60 ° angle of twist in the form of a tube with inside diameters of 1 to 30 mm and film thicknesses of 0.2 to 3 mm and extruded with the atomizing auxiliary medium in a quantity ratio of 0.5 to 10 kg per kg of melt, atomized to powder at a pressure of 5 to 100 atmospheres, a temperature of 20 to 35O ⁰ C and a speed of 200 to 700 m / sec by dividing the auxiliary atomization medium into two partial streams in a ratio of 1 5 3 to 3 : 1, let a partial flow act on the inside of the melt tube, while the outside of the tube is still guided over a length of 2 to 8 mm, then the second Partial flow can impinge concentrically on the outside of the melt tube at an angle of 15 to 70 ° to the tube axis and the gas flow is still 1 to 6 mm practically parallel to the tube axis.

The thermoplastic plastics produced according to the invention Methods that can be made into powders include, for example, polyolefins, polyamides, polyurethanes, and polyesters Polymers of styrene, o-methylstyrene andoG-methylstyrene.

Olefin polymers are preferred as thermoplastics for the process. Eb is also possible, mixtures of different to pulverize miscible thermoplastics.

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Suitable olefin polymers are above all the homopolymers of monoolefins having 2 to 4 carbon atoms. Both Polyethylenes preferably used come from the whole density

'Z

range from 0.915 to 0.960 g / cm in question. Are also suitable the copolymers of ethylene with olefins, such as propylene and butene-1, and copolymers of ethylene with other ethylenic unsaturated monomers, e.g. vinyl esters of saturated aliphatic monocarboxylic acids with 2 to 18 carbon atoms, Vinyl ethers, vinyl chloride, acrylic and methacrylic esters, which are derived from alkanols with 1 to 5 carbon atoms, and polymers from ethylene and acrylic acid esters, which are also free Contain acrylic acid groups, e.g. ethylene-tert-butyl acrylate-acrylic acid polymers. The proportion of comonomers in the total weight of the polymer can be up to 50 percent by weight. Even Chlorinated polyethylene can be used, as well as copolymers of isobutylene, up to 10 percent by weight 1,3-diolefins such as butadiene and isoprene contain.

The suitable for the process, polyamides are prepared for example by polymerization of lactams containing 6 or 12 ring carbon atoms or by polycondensation of aliphatic dicarboxylic acids such as adipic acid and sebacic acid, and aliphatic diamines having 6 to 15 carbon atoms.

Polymers with a wide molecular weight range, which is characterized by the melt index (according to ASTM D 1238-57 T) MIp 16/10 ° C. ^of 0.1 to 100, preferably 0.5 to 25, can be atomized by the process according to the invention. The addition of plasticizers or lubricants to improve the flowability is not necessary for the atomization of the melts by the process according to the invention. However, admixtures can be added to all of the products mentioned before atomization in order to achieve certain product properties or certain requirements for further processing, e.g. heat, light and UV stabilizers, furthermore flame retardants, dyes, fillers, e.g. wood flour, fine sand, chalk, Titanium dioxide and soot, as well as metal powder or chips and glass fibers. The proportion of admixtures in the

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Zen can be up to 70 percent by weight. The permissible particle sizes of the admixtures depend on their shape and the Dimension of the product nozzle. If the longitudinal dimension of the particles is approximately the same as the transverse dimension, the permissible is The maximum size of the particles is about half the width of the ring slot the product mouth. With transverse dimensions under 0.1 mm, the length can be up to approx. 10 mm. When atomizing thermoplastic melts, containing finely divided additions, powders are obtained in which the additives are homogeneously distributed.

In detail, the method according to the invention is carried out as follows: that the thermoplastics melted, in a conically tapered annular film flow, preferably with a swirl, for The nozzle mouth is conveyed and extruded in the form of a hose.

The operating conditions of the melt (speeds, pressures, Temperatures) can be defined as follows: The extrusion rate of the product is between 0.2 and 4, preferably between 1 and 2 m / sec, the product pressure between 5 and 300, preferably between 60 and 200 atmospheres. The melt temperature can be between the melting point and the maximum temperature permissible without chemical change (degradation) of the product lie. It is expedient to work close to the upper limit to achieve relatively low viscosities.

The cone angle <£ of the product flow according to the figure should be 5 to 40, preferably 15 to 25 °, based on the nozzle axis. The angle of twist to achieve a uniform circumference Film can be between 0 and 60 °, preferably between 15 and 45 °. The dimensions of the extruded tube are within the limits: internal diameter 1 to 30, preferably 3 to 15 mm, film thickness 0.2 to 3, preferably 0.5 to 1.5 mm.

Air and inert gases are primarily used as auxiliary atomization media or steam is used. The process is particularly economical when air is used as the auxiliary atomization medium. at the use of steam must adhere to the thermoplastic powder to be dried.

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The auxiliary medium used for atomization is divided into two partial flows in a ratio of 1: 3 to 3: 1, preferably 1: 1.5 divided up to 1.5: 1. These partial flows are guided in such a way that they reach the product hose emerging from the nozzle opening attack and atomize its inside and outside. In this way, there is a relatively large contact area between Product and auxiliary medium created. Since the auxiliary medium attacks both sides of the hose, it is only half the film thickness to penetrate for the purpose of atomization. The turbulence can be caused by opposing circumferential components (swirl) of the two gas flows and the shear gradient in the mouth area are increased. With the large contact area, the small penetration depth, the great turbulence and the high shear gradient create favorable conditions for energy-saving atomization.

The first partial gas flow, preferably the smaller one, is blown into the extruded product hose. The diameter this internal gas flow is generally 0 to 2, preferably 0.5 to 1 mm smaller than the inside diameter of the product hose. Before the product hose, the outer wall of its nozzle has left, the internal gas flow engages the freed product hose at. This point of attack is 2 to 8, preferably 3 to 5 mm behind the extrusion plane of the product hose back (internal gas reserve). The external gas stream, preferably the larger partial flow, is inflated concentrically on the outside of the product film at an angle β (according to the figure) to the nozzle axis, which is 10 to 30, preferably 15 to 25 larger than is the cone angle of the product flow. The thickness of the Outer gas ring is between 0.3 and 3, preferably between 0.5 and 2 mm. After it has attacked the product hose, the external gas flow is preferably still over a length of 1 to 6 from 2 to 4 mm from the external gas nozzle (external gas reservoir). If the two gas streams are provided with a swirl, so is the angle between the resulting speed vector gate and the DÜ3enachse (angle of twist) expediently not greater than 30 °, preferably less than 15 °> to train. In this case, the G has speed scope components of the two Gas flows preferably in the opposite direction. That = invention-- · according to. However, the process also works with swirl-free gas streams.

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The operating conditions for the auxiliary atomization medium depend to a large extent on the nozzle capacity (product throughput per time), as well as on the desired grain fineness. Pressures of A to 6 atmospheres for the auxiliary medium are sufficient if the nozzle capacity is up to approx. 30 kg / h. With a nozzle capacity of 200 to 300 kg / h, 30 to 50 atmospheres are required. The specific gas consumption increases from 1 to 2 to up to 4 kg of auxiliary medium per kg of product. If a very fine powder is required, the grain size of which should be, for example, 95 $> less than 50 μ , the gas pressure must be increased to 100 to 200 atmospheres under otherwise identical conditions or the specific gas consumption is increased to 10 to 20 kg of auxiliary medium per kg of product .

The achievable mean gas or steam speed in the mouth cross-sections at the specified pressures is usually between 0.8 and 0.95 times the speed of sound, ie, depending on the temperature of the auxiliary medium, between 300 and 400 m / sec. When using gas as the auxiliary medium temperatures between 20 and 35O ⁰ C can be used, preferably between 80 and 12O ⁰ C. The high gas temperatures of 150 to 35O ⁰ C are required only when the auxiliary medium, the heat for heating the sputtering apparatus must deliver. It is advisable to use electric heaters for this. When using steam as an auxiliary atomization medium with temperatures of 150 to 200 ^° C., the electric heating of the nozzles can be dispensed with.

Significant advantages of the method according to the invention in comparison to the known procedures are:

The specific energy requirement for the atomization of thermoplastic melts is about 50 ^ lower than with the known methods with qualitatively the same grain size. In addition to the use of inert gases as an auxiliary medium, air and steam can also be used. If air is used as the auxiliary atomization medium, the operating costs are further reduced. The susceptibility of the product mouth of the atomizing devices to clogging is considerably less. Therefore, melts containing pesticides up to approximately $ 70 can be atomized. 009846 / U59 -8-

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The general susceptibility to failure of the atomizing devices is lower because no back pressure of the melt enters the gas nozzle. The devices can be turned off several times and put them back into operation without having to be removed and cleaned every time. Multiple atomizers can be used can be used in parallel in a spray tower, which enables larger system capacities.

The method according to the invention is expediently used to carry out the process according to the invention a device which, as shown in the figure, consists essentially of three concentrically arranged nozzles, wherein the auxiliary atomization medium through the inner gas nozzle (1) with a diameter of 1 to 30 mm and the outer gas nozzle (3) with an annular gap width of 0.3 to 5 mm at an angle of ß = 15 to 70 to the nozzle axis and the plastic melted in an extruder through the product nozzle (2) with an annular gap width of 0.2 to 3 mm with a cone angle oC of 5 to 40, based on the nozzle axis, promoted and so in the mouth area of the three-flow nozzle so that the internal gas flow is at a distance of (χ) = 2 to 8 mm from the front edge of the mouth the product nozzle acts on the inside of the extruded product hose, while the mouth leading edge of the Outside gas nozzle protrudes by (y) = 1 to 6 mm over the front edge of the mouth of the product nozzle. The inner shielding sleeve (4) and the outer shielding sleeve (5) prevent the product from being cooled down too much by the mostly colder gas streams. The inner one The nozzle heater (6) and the outer nozzle heater (7) are used to set or maintain the optimum atomization temperature of the product. This temperature is set by the thermocouples (8) at the nozzle inlet and (9) just before the nozzle mouth of the product monitored. At (10) the internal gas is fed to the nozzle, at (11) the product and at (12) the external gas. Of the The opening cross-section (the gap width) of the product nozzle is set by the spacer ring (13), the opening gap width of the Outside gas nozzle through the spacer ring (14). The size (x) in the figure represents the rear opening of the inner gas nozzle, the Large (y) the orifice template of the gas nozzle opposite the Product nozzle. The cone angles of the mouth are also shown Product flow and ß of the exhaust gas flow

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on the nozzle axis. Centering collars in the cylindrical part ensure an exactly concentric alignment of the mouth cross-sections the nozzles or sleeves. These centering collars have a number of bores or slots to enable the flow provided, which may have an inclination in the circumferential direction to achieve a twist. While the diameter If these collar bores do not play a role, the condition exists for the total area of the bores or slots on a collar, that it must be larger than the area of the associated annular mouth gap, preferably by a factor of 1.2 to 4. If the inner gas is also to be provided with a swirl, a swirl body is inserted at the inner gas inlet of the nozzle (at (10)).

The areas of application of thermoplastic powders with and without admixtures extend over a very wide area. The powdery Thermoplastics are used, for example, in rotational sintering, and still in injection molding, especially for small parts for coatings, e.g. of carpet backing, metal surfaces (flame spraying) etc .. Thermoplastics with admixtures are used for dimensionally stable Larger parts are used, e.g. panels, in particular to improve the strength properties (addition of Glass fibers). Thermoplastic powder with high levels of coloring agent are better suited for uniform coloring of larger quantities of thermoplastics than the pure dyestuff. The same applies the metering in of stabilizers and other additives, in particular to prepare the thermoplastic for film production. If a large surface is required for the aftertreatment of a thermoplastic, then atomized one is used Powder is useful as an intermediate stage.

The grain sizes of the powder were determined by sieve analyzes with an air jet sieve.

example 1

A polyethylene with a density of 0.92 g / cm with a melt index of 18 (2.16 kg / l90 ° C.) and a melting point of HO ⁰ O is passed through a screw extruder and an electrically heated pipe to an atomizing device with a capacity of 30 kg / h

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promoted. The extruded product tube has a diameter of 4 mm and a thickness of 0.3 mm. The inner gas stream has a diameter of 3.5 mm, the annular outer gas stream a thickness of 0.4 mm. ^{Nitrogen at 200 °} C. and 8 atmospheric pressure is used as the auxiliary atomization medium. The ratio of external gas to internal gas is 1.2; the internal gas reserve (x) and the external gas reserve (y) are each 2 mm, the cone angle of the product flow ^ = 17.5, the cone angle of the external gas flow ß = 37.5 ° The melt is conveyed into the atomization device at 65 atmospheres and 280 C. and heated there to 300 ° C. With a specific gas consumption of 1 Nm per kg of product, the following grain size is achieved:

$ 80><£ 500 μ ; 60 # <300 µ ; 8 % -C 100 µ

Example 2

The external gas gap is enlarged to 0.5 mm compared to Example 1, so that there is now a specific gas consumption of 1.3 Nm / kg. In this case it is atomized with compressed air. at Otherwise, the same conditions as Example 1, a polyethylene powder of the following grain size is now obtained:

90 % ^ C 500 yes. ; $ 65> ^ - 300 yes. ; 10 # ^ 100 μ

Example 3

The external gas gap is enlarged to 0.7 mm compared to Example 1, so that the specific gas consumption is 3.3 Nm / kg increases. With otherwise unchanged operating conditions, the grain size of the polyethylene powder is:

97.5 Io-C 500/1; 82 # -C30Ou; 14 ^^.

Example 4

In the case of the atomizing device mentioned in Example 1

the external gas flow ß = 60 work " 009846/1459 -11-

worked with a cone angle of the external gas flow ß = 60

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as well as with the other oils according to Example 3. A coarser polyethylene powder is obtained in which 32 # of the particles> 500 are fixed

Example 5

On the atomizing device according to Example 1, the inner

gas reserve (x) and the outside gas reserve (y) enlarged to 5 mm,

If the polyethylene described in Example 1 is atomized, a grain with $ 30> 500 μ is obtained.

Example 6

Compared to Example 1, a ratio of external gas to internal gas of 0.4 is set. All other parameters remain unchanged. A polyethylene powder is obtained which has 50 % particles of a size greater than 500 μ.

The same result is obtained when the ratio of outside gas to inside gas is 2.7.

Example 7

The atomization device is set as in Example 1 and the same product is now with water vapor of 14 atu and one specific steam consumption of 2.5 kg / kg atomized. The grit obtained is as follows:

96 io ^ C 500 µ ; 76 <jo <300 μ ; 15 $> ^ 100 μ

To achieve the same grain spectrum with one atomizing nozzle without electrical heating, 18 atmospheres and 3 kg of steam are each kg of product required.

Example 8

* 2

VAn density 0 polyethylene, 'j? g / cn with a melt index of 5 is fed to the nozzle according to example 1. The required U before the delivery pressure of the melt is at 290 ⁰ C 120 atm. Atomized

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atm with nitrogen is between 15 and 160 ⁰ C, the specific gas consumption is 2 NNR / ^k · S ^The obtained grain size corresponds to that of Example 2. Fig.

Example 9

The polyethylene mentioned in Example 8 is supplied with 35 to 50 $ and various dyes with primary particles below 1 μ as a highly concentrated batch of the atomizing device described in Example 1 with an external gas gap setting of 0.5 mm and atomized under the following conditions: | Melt pressure 120 atmospheres, atm melt temperature 310 ⁰ C, gas pressure 20, gas temperature 35O ⁰ C, specific gas consumption 1.9 min / kg. The obtained grain spectrum 93 ? Ο «~ 500 μ; 70 $ - <300 µ; 20 ^ is independent of the concentration of the admixtures in the specified range.

Example 10

A melt with additions as in Example 9 is produced with a specific gas consumption of 4.5 Nm / kg, a gas temperature of 215 ° C and a gas pressure of 38 atmospheres. The higher energy expenditure results in significantly finer grain sizes than in the previous example:

99.5 10 <500 µ; 96 # «c 300 µ ; 50 fo -c 100, u

Example 11

A polyethylene of density 0.94 g / cm with a melt index of 0.9 and a carbon black content of 35 $ is atomized under the following conditions by means of the atomization device according to Example 1: melt temperature 260 C; Melt pressure 50 atm, nitrogen temperature 220 ^° C., nitrogen pressure 38 atm. With a specific gas consumption of 8 Nm / kg, the following grain size is achieved:

99 1 ° <£ - 500 µ ; 93 # <C ^ 00 / a; 55 # ^ - 100 / i

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A polyethylene of density 0.96 g / cm with a melt index of 6.5 of the sputtering apparatus of Example 1 is conveyed and sprayed with the following operational data: melt temperature 280 ⁰ C, melt pressure 130 atmospheres gauge, gas pressure 25 atm, gas temperature 130 ⁰ C, specific gas consumption 4 Nm / kg. The powder obtained has the following particle size distribution:

99 % <500 µ; 70 <? O <: 300 μ ; 20 # ^. 100 µ

Example 13

* 7

din polyethylene of density 0.96 g / cm with a melt index of 5 (2.16 kg / l90 ° C) and a melting point of 135 ° O is again via the screw extruder and an electrically heated pipe conveyed into an atomizing device with a capacity of 30 kg / h. In this, in contrast to Example 1, the melt not extruded in the form of a smooth hose, but as a hose with notches in the direction of flow. These shouts have a depth of 0.4 mm in the 0.6 mm thick tube, a width of 0.5 mm and a distance of also between them 0.5 mm. The melt temperature is 275 ° C. and the melt viscosity is 1.8. 10 poise. The delivery pressure of the melt is 80

(Nitrogen)

atü. The two gas flows / are at 10 atm in a quantitative ratio Outside gas to inside gas of 1.15 and at a temperature of 250 ° C in the nozzle. The quantitative ratio of gas to

• z

Product is 2 Nm / kg. A powder of the following grain size is obtained:

85 % <z 500 µ ; 45 $> -c 300 µ ; 5 # -C 100 µ

Example 14

Product and atomization device as in Example 13. Operating data the ijchmelze also unchanged. The doubling of the specific expenditure on 4 Nm ^ / kg at 20 atü gas pressure results a grain refinement to the following values:

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99.5 1 ° C 500 ^ u; 95 1 ° < 300 µ; 25 $ -c 100, u

Example 15

A polycaprolactam having a K value of 68-72 and a melt viscosity of 4000 poise at 25O ⁰ C is conveyed to the sputtering apparatus according to Example. 1 The "melt contains an addition of 40 % glass fibers (diameter 10 yd, length 1 to 4 mm). The product mouth hose has a thickness of 0.5 mm. The melt is conveyed into the atomizing ^{device at 50 atmospheres pressure and 30O 0 C} atomising gas of 2 atm and 14O ⁰ G. The specific gas consumption is 0.5 Nm / kg. The powder obtained has a needle-like structure with transverse dimensions between 0.1 and 0.5 mm and longitudinal dimensions of 0.5 to 2 mm.

Example 16

The polyethylene mentioned in Example 1 / a sputtering atmospheres of Capacity 100 kg · hr at 120 and conveyed 300 ⁰ G. The extruded melt tube has an inside diameter of 5 Eö.u and a thickness of 0.8 mm. The internal gas reserve (x) and the external gas reserve (y) are each 3 mm, the cone angles oC = 17.5 ° and ß = 37.5 °. The atomizing device has no electrical heaters. The temperature of the inner gas is 300 ⁰ C, the outdoor gas temperature 120 ⁰ C. The outer gas gap has a thickness of mm. 1 The gas pressure (here air) is 30 atmospheres inside and outside. The ratio of external gas to internal gas is 1.15, the specific gas consumption 3 Nm / kg. The following grain size is obtained:

95 1 » <: 500 μ; 84 f><: 300 μ ; 59 # ^ L 200 μ

Example 17

Atomizing device as in Example 16, as well as the operating conditions of the gas. A polyethylene with a density of 0.92 g / cm and a melt index of 5 is atomized at a melt ^{temperature of 30O 0 C and a melt pressure of 160 atmospheres.} The specific gas consumption is

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3 Nm / kg. The grain looks like this:

89 # ^ 500 Ji; 75 $ ^ c 400 µ ; 62 # <; 300 yu

Example 18

A polyethylene with a density of 0.92 g / cDr and a melt index of 18 is fed to an atomizing device with a capacity of 200 kg / h. The extruded tube has an inside diameter of 6 mm and a thickness of 1 mm. The inner gas trap position (x) and the outer gas blanket (y) are each 3.5 mm, the angles o6 = 17.5 ° and ß = 37.5 °. Since no electrical heaters are built into the nozzle, an internal gas temperature of 250 ⁰ O is used. The outside gas has a temperature of 80 C. The thickness of the outside gas ring flow is 1.2 mm. The gas ratio outside to inside is 1.2, the specific gas consumption 4.5 Nm / kg and the gas pressure 50 atm. The grain analysis has the following result:

93 1o <500 fx ; $ 71 ~ 300 ji; 23 $> ^ 100 μ

Example 19

The polyethylene according to Example 18 is atomized with an electrically heated atomization device with a capacity of 200 kg / h.The geometrical dimensions of the nozzle opening are as in Example 18, except for the outer gas ring gap, which is now set to 1 mm, which results in a specific gas consumption at 50 atmospheres gas pressure of 3.5 Nm / kg results. The gas temperature inside and outside is 80 ^° C. The same grain size as in Example 18 is achieved with significantly less energy consumption.

Example 20

The polyethylene according to Example 18 is fed to an electrically heated atomization device with a capacity of 300 kg / h. The dimensions of the extruded tube are 6.5 mm Inside diameter and 1.2 mm thickness. The size of the internal gas return

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position (χ) and the outside gas blanket (y) is 4 mm, the angle oc = 17.5 °, the angle ß = 37.5 °. The gas pressure is 50 atm, the gas temperature 80 ⁰ C inside and outside, the gas ratio outside ^ to inside 1.2. With a specific gas consumption of 3 Wm / kg, the following grain spectrum is obtained:

84 i <500 µ ; 55 1 ° < 300 / ι; 18 # -c 100 / i

Example 21

The procedure is as in Example 20 and an ethylene-yinylacetate copolymer the density 0.94 g / cm and the melt index 4 with a content of 14 $ vinyl acetate atomized. Man receives the following grain spectrum:

85 1o <500 yu; 57 ^ ^ 300 yu; 15 ^ V 100 / i

The properties of the material used were after spraying unchanged.

Example 22

Again, as in Example 20, and edn _; Ethylene-n-butyl acrylate copolymer with a density of 0.93 g / cm and a melt index of 2 with a content of 17% n-butyl acrylate was used. The following grain size results:

87 io - <500 ^ u; $ 57> «C 300 µ ; $ 16 , * £. 100 µ

After spraying, no change in the properties of the material used can be determined.

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Claims (2)

- 17 - O.Z. 26 145 Claims Process for the production of thermoplastic powders by extruding thermoplastic plastics and dividing the molten extrudate into a powder with the aid of a gas or vapor as an auxiliary atomization medium, characterized in that thermoplastics with temperatures between the melting point and the maximum temperature permissible without chemical change of the product are produced with pressures between 5 and 300 atmospheres and a muzzle velocity of 0.2 to 4 m / sec in a conically tapered annular flow of 5 to 40 ° cone angle and 0 to 60 ° angle of twist in the form of a tube with internal diameters of 1 to 30 mm and film thicknesses of 0, 2 to 3 mm and extruded with the atomizing auxiliary medium in a quantitative ratio of 0.5 to 10 kg per kg of melt, at a pressure of 5 to 100 atmospheres, a temperature of 20 to 350 ⁰ C and a speed of 200 to 700 m / sec atomized to powder by dividing the auxiliary atomization medium into two partial streams in a ratio of 1: 3 to 3: 1, allows a partial flow to act on the inside of the melt tube while the outside of the tube is still guided over a length of 2 to 8 mm, then the second partial flow concentrically on the outside of the melt tube at an angle of 15 to 70 ° to the tube axis can impinge and the gas flow is still 1 to 6 mm practically parallel to the hose axis. 2. Device for carrying out the method according to claim 1, characterized in that it consists essentially of three concentrically arranged nozzles according to the figure, the auxiliary atomization medium through the inner gas nozzle (l) of 1 to 30 mm in diameter and the outer gas nozzle (3) with a Ring gap width from 0.3 to. 5 mm at an angle of fö - 15 to 70 ° to the nozzle axis and the plastic melted in an extruder through the product nozzle (2) with an annular gap width of 0.2 to 3 mm with a cone angle CA of 5 to 40 °, based on the nozzle axis promoted and such in Münd-unga be rich dreiflutigen the nozzle are merged _r that the Γnnengasstrom at a distance of 00 9846 / U53 - 18 - - 18 - O.Z. 26 145 (χ) = 2 to 8 mm in front of the front edge of the mouth of the product nozzle the inside of the extruded product hose acts while the front edge of the mouth of the outside gas nozzle by (y) = 1 to Protrudes 6 mm beyond the front edge of the mouth of the product nozzle. Sign. Badische Anilin- & Soda-Fabrik AG- ■ κ 009846/1459