WO2000071319A1 - Method for preparing or treating a thermoplastic material and device for carrying out said method - Google Patents

Abstract

The invention relates to a method for treating and/or preparing a thermoplastic material, in particular, resin binding agents for powder lacquers, such as polyesters, polyepoxides or polyacrylates, or powder lacquers which are not cross-linked, by a cooling process in a treatment line for forming granulates. The invention also relates to a device for carrying out said method, comprising a substantially tubular treatment line, containing one or more sections which can be heated or cooled. Said treatment line comprises circulating devices or inserts and/or a conveyer. The treatment line which is closed in a known manner is connected at one end to a reactor (20) or extruder, under exclusion of the atmosphere, and a cutting device is located at the outlet end (3, 103) of said reactor or extruder.

Description

Process for preparing and / or preparing a thermoplastic composition and device for carrying out the process

The invention relates to a method for the preparation and / or preparation of a thermoplastic composition, in particular resin binders for powder coatings, such as polyesters, polyepoxides or polyacrylates, or uncrosslinked powder coatings, with cooling in a treatment section for granulate molding

DE 21 43 184 B2 discloses a device having a housing with a screw rotatably arranged therein for processing polymeric plastic masses, optionally with additives, the housing being open at both ends for the purpose of the material inlet and outlet. This device is particularly suitable for homogeneous Distribution of any additives in the polymeric plastic mass The device, into which solids are added via metering arrangements, furthermore comprises heating and cooling devices which are divided into zones, so that the viscosity of the mass desired for homogeneous mixing can be achieved

From DE 19 12 321 B ιst a device for plasticizing plastic granules is known, which comprises a hollow cylindrical housing, in each of which a Ford screw and a plasticizing rotor extending in its longitudinal axis are arranged. During the plasticizing process, a complete removal of released volatile substances should be ensured , the removal of which is still required by suction, partial vacuum, etc., whereby the disadvantageous environmental relevance of releasing volatile components from hot plastic masses is not dealt with. Furthermore, DE 19 12 321 B does not provide any information about emission-free cooling of hot thermoplastic melts as well via a further treatment of the mass after plasticization or via a final granulate formation

DE 26 54 774 B2 discloses a screw machine for the homogenization of molten polymers, in particular high-pressure polyethylene. This machine comprises a multi-shot housing with several cooling zones and screws arranged in its bore. Special feed openings guide water as cooling medium towards the flow of the polyethylene melt and via a special one The water or its steam is drawn off again. The guidance of the cooling water and the design of the screw machine described in this document loosen the surface of the melt of the polymer and to penetrate the polymer through the water, which on the one hand cools the melt and on the other hand essentially turns the water into the vapor state. After homogenization, the melt is pressed out through the extrusion die and optionally further processed into granules

This procedure, which emerges from DE 26 54 774 B2, is very specifically geared to the homogenization of molten polyethylene, cooling of the melt by direct contact with water being possible in this form only as a result of the hydrophobicity of the polyethylene. This is the teaching of DE 26 54 774 B2 not suitable for eliminating the considerable disadvantages inherent in the prior art for the preparation and / or preparation of thermoplastic compositions, in particular resin binders such as polyester, polyepoxides or polyacrylates. In contrast to polyethylene, these thermoplastic compositions do not have their hydrophobicity, with Polvester, for example, above In addition, especially at the high temperatures in question here, they are by no means indifferent to water. Instead, they experience degradation to their starting materials, essentially dicarboxylic acids and diols. Finally, DE 26 54 774 B2 does not provide any further details on the given situation As a further processing of the pressed homogenized polyethylene mass made into granules

In addition, a method and a device of the type mentioned at the outset for producing granules of a resin binder are known from the prior art. Molten resin is transferred from a reactor vessel to a water-cooled cooling belt and the solidified resin is then broken up on a crusher a broad distribution of grain sizes on the process and the device according to this prior art, however, have considerable disadvantages. On the one hand, submersible products can escape from the melted resin applied to the cooling belt and pollute the environment , and in addition, a high level of dust occurs when breaking

EP 0 548 896 A1 discloses the production of pills of a binder from the melt by means of a pastil preparation, which is not defined in more detail, the pills being comminuted after cooling the particle size distribution between 0.001 and 5.5 mm is still relatively wide and the crushing of the pills is associated with dust development The object of the invention is to provide a method and a device for preparing and / or preparing a thermoplastic composition, in particular resin binders for powder coatings, such as polyesters, polyepoxides or polyacrylates, or uncrosslinked powder coatings for molding granules, which above all have the disadvantages of the prior art described above Technology not adhering to The essential goals of the invention are to work under extremely environmentally friendly conditions and to achieve a grain size distribution of the granulate produced in a very narrow range just below and above a value between 1 and 3 mm in a proportion of approximately 100%

This object is achieved according to the method according to the invention in that the mass is supplied in liquid form with the atmosphere closed to the treatment section and further cooled in the atmosphere and circulation to a temperature> glass transition area (Tg) which is above room temperature is, where appropriate, one or more additive (s) and / or one or more further component (s) is (are) added to the mass in the treatment line, and that the mass emerging from the treatment line in still plastic form is then cut into small pieces of granulate from which their residual heat is removed before storage.

The advantage of the method according to the invention is that no sublimation products can escape from the mass during its preparation and / or preparation by working under exclusion of the atmosphere. In addition, breaking or comminuting the solidified mass or mass particles is unnecessary, so that no dust is generated Furthermore, an increase in the debris density of the granulate and thus a better utilization of containers, but above all an increase in the constancy of the debris density can be achieved

A special embodiment of the invention is that the treatment section extends in the vertical direction, the temperature gradient running from top to bottom. In this arrangement, gravity contributes to the mass through the treatment section. However, this is distributed in a particularly advantageous manner Arrange the mass particularly evenly across the cross-section of the treatment section, which results in a very effective treatment of the mass

According to the invention it is further provided that the resin binder mass of the treatment section with a temperature between 140 ° and 300 ° C or uncrosslinked powder coatings with a temperature between 90 ° and 140 ° C and until the end of Treatment section is cooled to a temperature between 5 ° and 50 ° C, preferably 10 ° and 30 ° C above Tg.

In order to improve the processability of the mass, the mass can be heated over a distance after it has been introduced into the treatment section and / or can be kept at the reactor or extruder temperature. Only then is the mass subjected to cooling. This cooling, which is preferably carried out in separately controllable process sections, has the advantage that one or more additive (s) and / or one or more further component (s) are added to the mass in the treatment section in a very individually controlled manner, taking into account the most favorable temperature and viscosity conditions can (can).

The invention also relates to a device for carrying out the method with an essentially tubular treatment section having one or more coolable section (s) with circulating devices or internals and / or a conveyor, the device being characterized in that the in in a known manner, a closed treatment section is connected at one end to the atmosphere of a reactor or extruder, and after the outlet end a cutting device is arranged, and that the treatment section is equipped with cooling to produce a temperature gradient from its entrance to the outlet to a temperature> glass transition area (Tg) of the thermoplastic mass is provided, the glass transition area (Tg) being above room temperature.

With the help of such a device, granulate of a thermoplastic material with a uniform, very narrowly defined particle size distribution can be generated by eliminating factors that are harmful to the environment. Here, both a cooling belt and a crusher for grinding solidified masses or mass particles according to the known prior art can be omitted. Furthermore, an increase in the bulk density of the granulate and thus a better utilization of containers, but above all an increase in the constancy of the bulk density can be achieved. It is particularly advantageous if the treatment section is arranged vertically. in order to make full use of the promotional effect of gravity and thereby ensure problem-free discharge of the mass to be prepared or prepared. In a particularly advantageous manner, however, with this arrangement, the mass is distributed particularly uniformly over the cross section of the treatment section, as a result of which the mass is treated very effectively. According to a further embodiment of the device according to the invention, the treatment section has an extruder and / or compounder and / or static mixer or mixer-heat exchanger. Advantageously, an extruder is always used in the cooler zones of the treatment section, whereas in the area of the entrance to the treatment section a static mixer can also be arranged in the adjoining heating zone. However, it should advantageously be possible to heat and cool any temperature zones as desired. However, the treatment section according to the invention can also have one or more dynamic mixers or mixer-heat exchangers

10 According to a further feature of the invention, it is provided that individual sections of the treatment section heating / cooling devices are assigned, each with individually controllable, possibly indirect control loops. As a result, individual areas of the treatment section can be heated and cooled effectively and in a simple manner as required and thus also control the viscosity of the mass to be prepared or prepared in certain sections of the treatment section

Another feature of the invention is that one or more feed lines for feeding additives and or other components for incorporation into the thermoplastic mass flow into the treatment line, preferably fed via metering pumps, by opening the feed line (s) into sections of the treatment line With precisely adjustable temperature and thus in areas of the mass with the desired viscosity, a more flexible metering, for example of liquid additives but also other material components, is possible, whereby optimal conditions for the preparation and / or preparation of a thermoplastic mass to form the granulate can also be achieved

In the drawing, a device according to the invention is illustrated in more detail by means of two exemplary embodiments, in which FIG. 1 shows a schematic representation of a device arrangement and FIG. 2 shows a further example, for example

.0 show leadership form of a device according to the invention

The device according to FIG. 1 comprises an essentially tubular, closed treatment section for a thermoplastic composition to be prepared or prepared and has a vertically arranged extruder 1 which connects with its feed 2 to a reactor (not shown) and at the discharge end 3 thereof a cutting device (not shown) The extruder is equipped with a conveyor 4, eg screw conveyor, twin screw, etc. The introduction of the thermoplastic composition, in this case a resin, from the reactor into the feed 2 of the extruder 1 takes place at approximately 240 ° C. and the discharge from the extruder 1 at a delivery temperature of approximately 20 ° C. above the glass transition temperature (Tg).

The extruder 1 has various sections, namely a section 5 in the area immediately following the feeder 2, in which section 5 the resin introduced is kept at a reactor temperature of approximately 240 ° C. This area of the extruder can also be replaced by a static mixer or mixer heat exchanger. Subsequently, the extruder 1 comprises further, cooled sections 6, 7 and 8 with a falling temperature level.

A filter for removing foreign particles can be arranged in a manner not shown between the reactor and the intake into the treatment section and / or also within the treatment section, preferably between the first section 5 or static mixer and the beginning of the cooled sections 6, 7 and 8 of the extruder 1 .

The extruder 1 has a double jacket, heating or cooling medium being able to be introduced into the space between the jacket walls. For this purpose, in the area of the first section 5 there are a feed line 9 and a drain line 10 for the heating medium, for example thermal oil, and in each case in the area of the cooling zones 6, 7, 8 feed lines 11, 12, 13 and drain lines 14, 15, 16 for the cooling medium, for example water, comprehensive, separately controllable indirect control circuits are provided.

Dosing pumps 17, 18, 19 with their own control circuits are provided between the first section 5 and the following individual cooled sections 6, 7, 8.

At the outlet 3, the resin is discharged from the extruder 1 at a discharge temperature of approximately 20 ° C. above Tg. The still plastic discharge is cut into prismatic pieces by means of a cutting device, not shown, arranged directly at the outlet 3, so that Almost 100% of the granules obtained are granules with a very uniform and narrowly defined grain size, with a grain size distribution just below and above a value between 1 and 3 mm.

The method and, for example, a further embodiment of a device according to the invention for carrying out the method are explained in more detail using the following exemplary embodiments. Example 1:

1800 kg of a carboxylated polyester resin A, composed of terephthalic acid (35.9 mol%), 2,2-dimethylpropanediol 1.3 (43.6 mol%), ethanediol (5.1 mol%), adipic acid (2.5 Mol%) and isophthalic acid (12.9 mol%) with an acid number of 34.3 mg KOH / g polyester resin, a glass transition temperature of approx. 55 ° C (onset, 20 ° C / minute) and a viscosity of 4600 mPas.s at 200 ° C (ICI Cone & Plate) with a melt temperature of 240 ° C in a reactor 20.

The drain port of the reactor 20 is connected via a thermal oil-heated pump 21 (manufactured by Stork) to a treatment section which consists of a combination of a static 105 with three dynamic mixer heat exchangers in accordance with the three process sections 106, 107 and 108: the temperature is 240 ° C. Polyester resin is first fed through an inlet 102 to the mixer heat exchanger 105 (DN 80 mm, total length 1000 mm, from Sulzer). A filter can be installed between the pump 21 and the mixer heat exchanger 105 in a manner not shown.

After the resin has passed through the mixer heat exchanger 105, it is transferred into the feed area 100 of a three-shot extruder 101 (diameter 150 mm each) with a process length of 920 mm each.

At the transition pieces of the respective process sections 105, 100, 106, 107 and 108, intermediate rings 22 to 26 are arranged, which are conventional options (volumetric and / or gravimetric metering for solid and or liquid) for metering in liquid and / or have solid components for the preparation of preparations, temperature measuring points also being present. Components can also be metered in at the inlet 102 or in the mixer heat exchanger 105.

The extruder 101 is equipped with very good cooling capacities, and there is sufficient well water with a constant flow temperature of approximately 11 ° C. The respective process sections 100, 106, 107 and 108 are equipped with individually controllable indirect circuits (via GWK heating and cooling devices) 27, 28, 29 and 30; the heating / cooling medium is water and the mixer heat exchanger 105 is also cooled with water, which is heated to 65 ° C. via its own heating / cooling device 31. The polyester resin A is required with a mass flow of 150 kg / h over the treatment line; it emerges from the mixer heat exchanger 105 at 155 ° C., from the first process section 106 of the extruder 101 at 115 ° C., from the second process section 107 at 83 ° C. and from the third process section 108 via a special

. pull out discharge unit 103, which is provided with corresponding bores, at 74 ° C. The strands are cut directly at the outlet by a cooled rotating knife and are conveyed over a cooled surface until the glass transition temperature is undershot, air being at a temperature of approx. 12 ° C is blown in to accelerate the cooling process. That way

) produced pπ-shaped strand granulate has a diameter of approximately 1.6 mm and a length of approximately 2 mm

This granulate is then transferred to a pneumatic conveying section 32 and transported away. A conventional cyclone 33 is used to separate the granulate-air mixture. The granulate is then filled directly into a big bag 34

Embodiment 2 '

After preparation of about 620 kg of polyester resin A in the manner described in embodiment 1, an acrylic resin, Acronal® 4F (from BASF), which is customary as a leveling additive according to the prior art and which had been preheated to 85 ° C., is applied via a metering pump Connection to the intermediate ring 22 between the mixer heat exchanger 105 and the subsequent extruder 101 in the proportion of 5 1 part of acrylic resin to 9 parts of polyester resin A added. The 10% preparation of Acronal® 4F in this way prepared in polyester resin (→ masterbatch) falls after an identical treatment Course of the treatment section with practically the same granule size as the preparation form of the polyester resin A previously produced The measured outlet temperatures are 148 ° C (mixer heat exchanger 105), 109 ° C (end of process section 106), 81 ° C (end of process section 107) and 72 ° C (end of process section 108)

Embodiment 3

, While changing the proportions given in Example 2 when metering Acronal® 4F into polyester resin A, the amount added is reduced from 10% to 1.0% in this experiment [= polyester resin B] The mass flow of the polyester resin A from the reactor 20 remains unchanged. The additives Primid, Benzoin and Titanium dioxide given in the table below are premixed and added in constant proportion to the existing mass flow (60% polyester resin B, 40% additives according to the table).

No raw material%

1 Primid®XL 552 (from EMS Chemie) 9.3

2 benzoin 0.6 3 titanium 2310 (from Kronos) 90.1

Total 100

The third intermediate ring 24 (transition from process section 106 to process section 107) is selected for feeding into the discharge system. The remaining active remaining process length is sufficient to sufficiently disperse the added substances in polyester resin B. The temperature level is as follows: The material enters the first process section 106 of the extruder 101 from the mixer heat exchanger 105 at 155 ° C. via the extruder feed. The temperature is set via the heating / cooling devices 27, 28, 29 and 30. The mass has a temperature of 133 ° C. when it leaves the second process section 107. The additives mentioned at the beginning are added at this temperature. The temperature transition from the second process section 107 to the third process section 108 is deliberately selected such that a temperature of 110 ° C. prevails at the process section 108 when the intermediate ring 25 is reached. The discharge temperature at the discharge unit 103 is 74 ° C. The strands are processed further as described above.

After cooling, the granules obtained are ground and sieved to a particle size of <90 μm. The paint test is carried out on yellow chromated aluminum sheets AI Mg 1 F 13, mill finish, thickness 0.7 mm, at a baking temperature of 180 ° C and a baking time of 10 minutes (object temperature). The paint film thickness is around 80 μm. The coatings obtained show trouble-free surfaces (high gloss and very good flow) and pass the ball impact test in accordance with ASTM D 2794, ball diameter 1/2 inch, at 20 inch pound (reverse impact). Embodiment 4

In a modification of exemplary embodiment 3, the additive Byk®-361 (BYK-Chemie GmbH) is used in this experiment instead of Acronal® 4F [polyester resin C], and the addition of titanium dioxide is also omitted

The mass flow of the polyester resin A from the reactor 20 remains unchanged. The additives Primid and Benzoin specified in the table below are premixed and added in constant proportion to the existing mass flow (94.7% polyester resin C, 5.3% additives according to the table)

No raw material%

1 Primid® XL 552 (from EMS Chemie) 94 2 Benzoin 6

Total 100

The third intermediate ring 24 (transition from process section 106 to process section 107) is selected for feeding into the discharge system. The remaining active remaining process length is sufficient to adequately disperse the added substances in the polyester resin C. The temperature level is as follows: The material exits the mixer heat exchanger 105 at 155 ° C. via the extruder feed 100 into the first process section 106 of the extruder 101 The temperature is set via the heating and cooling devices 27, 28 so that the mass had a temperature of 128 ° C. when it left the first process section 106 of the extruder 101. At this temperature, additives mentioned at the outset were added. The temperature transition from the second process section 107 into the third process section 108 is deliberately selected such that a temperature of 98 ° C. prevails on the third process section 108 when the intermediate ring 25 is reached. The discharge temperature at the discharge unit 103 is 73 ° C. The strands are processed further in the same way as already described

After cooling, the granules obtained are ground and sieved to a particle size of <90 μm. The paint test is carried out on yellow-chromated aluminum sheets Al Mg 1 F 13, mill finish, thickness 0.7 mm, at a baking temperature of 180 ° C and a burn-in time of 10 minutes (object temperature). The paint film thickness is around 85 μm. The coatings obtained show trouble-free surfaces (high gloss and very good flow) and pass the spherical impact test according to ASTM D 2794, ball diameter 1/2 inch, at 20 inch pound (reverse impact).

Claims

claims 1 Process for the preparation and / or preparation of a thermoplastic composition, in particular resin binders for powder coatings, such as polyesters, polyepoxides or polyacrylates, or uncrosslinked powder coatings, with cooling in a treatment section for granule formation, characterized in that the composition is in liquid form at the end fed to the atmosphere of the treatment line and further cooled in the atmosphere and circulation to a temperature> glass transition area (Tg) which is above room temperature, the mass in the treatment line possibly one or more additive (s) and / or one or several other component (s) is (are) added, and that the mass emerging from the treatment section in still plastic form is then cut into granulate pieces, from which their residual heat is removed before storage. 2 The method according to claim 1, characterized in that the treatment section extends in the vertical direction, the temperature gradient running from top to bottom 3 The method according to claim 1 or 2, characterized in that the resin binder is fed to the treatment section at a temperature between 140 ° and 300 ° C or uncrosslinked powder coating materials at a temperature between 90 ° and 140 ° C and to the end of the treatment section at a temperature between 5 ° and 50 ° C, preferably 10 ° and 30 ° C over Tg or are cooled 4 Device for performing the method according to one of claims 1 to 3, with an essentially tubular, one or more coolable section (s) having treatment section with rolling devices or internals and / or a conveyor, characterized in that the in a well-known way closed treatment line is connected at one end to the atmosphere to a reactor (20) or extruder and after the outlet end (3, 103) a cutting device is arranged and that the treatment line with cooling to generate a temperature gradient from its entrance (2, 102) is provided at the outlet (3, 103) to a temperature> glass transition area (Tg) of the thermoplastic composition, the glass transition area (Tg) being above room temperature. 5 Apparatus according to claim 4, characterized in that the treatment section is arranged vertically. 6 Apparatus according to claim 4 or 5, characterized in that the treatment section has an extruder (1, 101) and / or compounder. 7 Apparatus according to claim 4 or 5, characterized in that the treatment section has a static mixer (5) or mixer heat exchanger (105). 8 Apparatus according to claim 4 or 5, characterized in that the treatment section has one or more dynamic mixers or mixer heat exchangers. 9 Device according to claim 8, characterized in that the individual sections (5, 6, 7, 8, 105, 106, 107, 108) of the treatment section heating-cooling devices (9, 10, 1 1, 14, 12, 15, 13th , 16, 27, 28, 29, 30, 31), each with individually controllable, possibly indirect control loops. 10 Device according to one of claims 4 to 8, characterized in that one or more feed lines for feeding additives and / or further components for incorporation into the thermoplastic mass open into the treatment section, preferably fed in each case via metering pumps.