DE2116940B1 - METHOD AND DEVICE FOR EXTRUSION OF PROFILE STRIPS FROM A THERMOPLASTIC - Google Patents

Description

There is a decisive advantage of this measure according to the invention in the fact that only a single plastic is used, what the machine and material expenditure considerably reduced. Requirement is however, a special selection of the relationships between the plasticizing temperature and the evaporation temperature of the propellant. By dividing the plasticized Plastic strand within the tool there is the possibility of one strand to be treated differently from the treatment of the other strand, d. H. particularly to get both strands at different temperatures. The one warmed higher The strand becomes foaming after the evaporation point of the blowing agent has been exceeded brought, while the plastic of the or the other partial strands remains unfoamed. If the two or more sub-strands are then brought together again, this results an intimate cohesive connection between the partial strands, which means additional Measures to connect the bodies formed therefrom are not required.

It is within the scope of the expedient development of the invention, that the substream forming the core is heated to the higher temperature and foamed is, so that a profile with a dense, solid outer jacket and a foamed, light Core results. The thickness of the outer jacket can meet the requirements of the respective desired product can be largely adapted.

Another alternative is that the one forming the jacket Partial flow is heated to the higher temperature and foamed.

In addition, the invention is concerned with a device for Carrying out the method with an injection molding tool, which is characterized is that the injection molding tool has at least two separate channels for the plasticized Has plastic, which open together into the coating nozzle and that at least one channel, one the plastic located in it, to the increased evaporation temperature of the propellant heating device is assigned.

In this way the conditions for a different Treatment of the two parts flows into one and the same. Plastic in the tool created. Both substreams can come from one and the same extruder. It is but it is also possible to use the same starting material from two different extruders refer to. The temperature of the two partial flows is in the area where they come together, d. H. at the coating nozzle so high that they merge into one another and thus enter into a cohesive connection with one another.

In further development. of the invention it is with the device. - It is expedient that two separate channels are arranged one inside the other and / or next to one another are. Another alternative provides that several pairs of nested Channels are arranged side by side .--- This - configuration is closely related with the shape of the profiles to be produced. The simple nested arrangement of two Channels leads to a simple, closed profile, the inner core of which is more dense or less dense than the surrounding outer jacket. In the other case, you can Form diverse profile shapes, for example running rails with several Foam parts that are connected to one another by stiffening solid parts.

In the device, it is appropriate that the the heater exhibiting part of the channel wall is arranged in a thermally insulated manner in the injection molding tool, to prevent the increased temperature from spreading to the other channel and thereby preventing unwanted foaming of this partial flow. This can be on the one hand by reducing the contact areas between the tool and in this reach the components forming the channels. On the other hand, these Components can also be thermally separated from one another by inserting insulating layers.

According to another development of the invention, in which the heating device having a channel the partial flow into numerous other partial flows of small Cross-section dividing device, in particular a sieve arranged. This lets the temperature applied by the heating device increases particularly easily transferred the material forming the corresponding partial flow, so that this largely foams evenly. Instead of the holes in the sieve, numerous narrow slits kick.

It has proven to be particularly advantageous that the sieve has a downstream flow nozzle opening into the jacket nozzle.

The confluence of the partial flow subjected to a foaming process should therefore be made in the form of a nozzle to prevent further evaporation of the propellant to allow under the influence of temperature and the pressure reduction within the nozzle.

After exiting this flow nozzle into the sheath nozzle the partial flow, which has already been foamed to a greater or lesser extent, lays itself to the outer, made of non-foamed plastic jacket under the pressure of the propellant on, so that a cohesive connection is created between the two partial flows.

It is also advantageous in the device that to the jacket nozzle a coolable calibration device is connected. This will result in a profile with a denser outer jacket this counteracts that of the foamed core Print cools and hardens quickly.

The finished molded body is finally through a subsequent Pull-off device continuously withdrawn from the tool.

The method according to the invention and that intended for its implementation Devices are not only suitable for the production of round profiles or such profiles, which have a uniformly thick jacket around the core. Rather, it is possible to achieve more angular profile cross-sections or profiles with one or more produce concurrent outer ribs.

The invention is shown below on the basis of a preferred embodiment and explained in more detail with reference to the drawing. 1 shows a longitudinal section by an injection mold for the production of a professional strand with a round cross-section with a denser outer jacket compared to the foamed core, roughly in the section along the line I-I in Fig. 2, Fig. 2 is an end view of the tool from the jacketing nozzle her and F i g. 3, 4 and 5 different ones produced according to the method and the device Profile shapes.

The tool consists of several concentric according to FIGS. 1 and 2 one within the other or axially one behind the other arranged parts. To the Not shown extruder includes a brake cone 1, which at a distance from one Flange piece 2 is included. In the brake cone 1 is an inner channel 3 of circle ~ shaped cross-section. Between the brake cone 1 and the flange piece 2, an outer channel 4 of circular cross-section is arranged. Axially up The brake cone 1 is followed by the core piece 5, in which the inner channel 3 continues is. This core piece 5 receives a cylindrical screen 6 in which the cross section of the inner channel 3 is broken down into a plurality of small cross-sections. The screen 6 is followed by a sleeve-shaped flow nozzle 7, which in the Mouth 8 opens into the sheathing nozzle 9 The core piece 5 is of an intermediate piece 10 surrounded at a distance. One of the outer walls of the core piece is in the cavity 11 5 adjacent heating jacket 12 is arranged, the heat energy through the holes 13 is supplied. On the outside of the core piece 5 and the intermediate piece 10 the outer channel 4 is guided along, the piece 14 of the outer end of the Injection tool is enclosed and a kink at the level of the flow nozzle 7 inwardly, so that it is concentric in the region of the mouth 8 of the flow nozzle 7 around this opens into the coating nozzle 9.

The tool is provided with two further heating bands 15 and 16, if necessary to maintain the plasticizing temperature of the plastic serve in the outer channel 4.

A known per se connects to the sheathing nozzle 9 therefore not shown in detail shown externally cooled calibration device at.

The operation of the device and the process steps are the following: The plasticized one supplied from an extruder not shown Plastic enters the inner channel 3 and to the other part in the direction of arrow 17 into the outer channel 4. The plastic located in the inner channel 3 flows up to the sieve 6 and is cut there in numerous substreams of small cross-section disassembled. This area of the core piece 5 is made so strong by the heating device 12 warms that the plasticized plastic is above the vaporization point of the in it Propellant contained is heated.

Due to the well-structured surface of the plastic, the Foaming occurs in the entire plastic stream and is intensified when this reaches the flow nozzle 7. If the plastic leaves the flow nozzle 7 at its mouth 8 and if it reaches the coating nozzle 9, then the foaming process is not yet finished.

The partial flow of the same flowing along in the outer channel 4 Plastic is obtained there at around the inlet temperature, but that in each Case is below the evaporation temperature of the propellant contained in it. This partial flow opens into one that surrounds the mouth 8 of the flow nozzle 7 Ring 18 into the coating nozzle and immediately comes into intimate contact with it the foamed partial flow in the inner channel 3. This is due to the ongoing Volume increase due to evaporation of the propellant on the outer wall 19 of the coating nozzle 9 pressed.

The two plastic streams merge intimately with one another. In the subsequent externally cooled calibration device, above all the outer, denser jacket of the profile produced in this way cools and hardens.

The reverse of this procedure is readily possible, and indeed in such a way that the plastic part flow contained in the inner channel 3 at a Temperature is kept below the evaporation point of its propellant, while at the same time the current in the outer channel 4 by appropriate heating the channel wall to a temperature above the evaporation point of the propellant is heated and thus foams. The foamed partial flow then settles in the area the coating nozzle9 as a jacket around the non-foamed and therefore denser core.

Fig. 3 shows a closed bar profile with one of the outer jacket 20 enclosed core 21, namely the core 21 from the through the inner channel 3 supplied and foamed partial flow of the plastic formed while the outer jacket 20 to the plastic partial flow fed through the outer channel 4 arises.

Both are intimate in the area of the separation zone 22, i. H.

firmly connected to each other. In place of the round bar profile Of course, a different profile shape can also occur.

The F i g. 4 shows a round rod with a core 21 'made of non-foamed Plastic, while the outer jacket 20 'is made of the same material, but less Density, exists.

F i g. 5 shows a profile which can be used as a curtain rail Can be found. This has three cores 21 ″ next to one another, which are made of foamed Consist of plastic and each of a sheath 20 "of the same plastic, however unfoamed, are enclosed. These three sub-profiles are made by bridges 23 made of the same non-foamed material connected to each other without achieve further by appropriate design of the injection molding tool of the device leaves.

Claims (10)

Claims: 1. A method for extruding profile strands made of a thermoplastic, with cross-sectional areas of different density, wherein these areas of different density alternatively around one another, next to one another or one above the other are arranged, using a foamable plastic and a propellant, its evaporation temperature above the plasticizing temperature of the plastic is, characterized in that the plastic flow at least temporarily in at least two partial flows are divided and brought together again before being pressed out, wherein at least one of the substreams at or above the evaporation temperature of the propellant heated and the or the other substreams at a temperature below the evaporation temperature of the propellant are kept. 2. The method according to claim 1, characterized in that the the Core-forming partial flow is heated to the higher temperature and foamed. 3. The method according to claim 1, characterized in that the the Sheath-forming partial flow is heated to the higher temperature and foamed. 4. Device for performing the method according to one of the claims 1 to 3, with an injection tool, characterized in that the injection tool has at least two separate channels (3, 4) for the plastic, which are common open into the jacket nozzle (9), and that at least one channel (3) one the plastic in it to the increased evaporation temperature of the propellant warming heater (12) is assigned. 5. Apparatus according to claim 4, characterized in that two separate channels (3, 4) are arranged one inside the other and / or next to one another. 6. Apparatus according to claim 4 or 5, characterized in that several pairs of nested channels (3, 4) arranged side by side are. 7. Device according to one of claims 4 to 6, characterized in that that the heating device (12) having part - the channel wall is thermally insulated is arranged in the injection molding tool. 8. Device according to one of claims 4 to 7, characterized in that that in the duct having the heating device (12), one divides the partial flow into numerous Device dividing further partial flows of small cross-section, in particular a sieve (6) is arranged. 9. Apparatus according to claim 8, characterized in that the sieve (6) is followed by a flow nozzle (7) opening into the jacket nozzle (9) is. 10. Device according to one of claims 4 to 9, characterized in that that a coolable calibration device is connected to the sheathing nozzle (9) is. The invention relates to a method for extrusion of Profile strands made of a thermoplastic, with different cross-sectional areas Density, these areas of different density optionally around one another, next to one another or are arranged one above the other, using a foamable plastic and a blowing agent, the evaporation temperature of which is above the plasticizing temperature of the plastic lies. As a rule, it is important to produce plastic profiles that to a more or less expanded core, an unfoamed, dense, have smooth, mechanically stronger jacket or to produce profiles which are made of are the same as two or more layers lying one above the other or next to one another Materials consist of different densities. For this purpose it is already from the German patent specification 1154264 known to use a spray head with nested nozzles to two to process chemically different plastics, of which only one, which exits through the inner nozzle is foamable. Such a known arrangement however, it has the disadvantage that separate machine devices are used for each of the two plastics are ready to be provided. In addition, it forms in the known methods and devices the foam core is often only made within a cooled calibration device, so that a material connection between the foamed core and the tight Coat is not possible. In these cases, therefore, the core must go through with the cladding an adhesive layer must be connected, which in turn requires additional machinery. Plastic profiles with a compression compared to the foamed core Outer sheaths are used, for example, in the furniture industry, but also in other industries as components into consideration. But there is also the important reverse Case that you need profiles with those above a guarantee of the necessary strength dense core a comparatively looser foamed shell is applied, for example for use as a braiding material. Such profiles, in which the foamed Areas are arranged around a dense core, can with the known device according to the German patent specification 1 154264 not be produced The invention is therefore the underlying task, professional ranks with different in the coat and in the core Establish density regardless of whether the areas are larger or smaller Are arranged tight inside or outside, get by with a single machine unit. In order to solve this task, one method is the one at the beginning mentioned type provided according to the invention that the plastic flow at least temporarily divided into at least two partial flows and again before being pressed out is brought together, with at least one of the substreams at or above the evaporation temperature of the propellant is heated and the other substream or streams are at one temperature be kept below the evaporation temperature of the propellant.