DE102014007280A1 - Method for mixing reactive components - Google Patents

Abstract

The invention relates to a method for mixing reactive components in a mixing chamber (1) having mixing head (2), wherein the mixing head (2) on the input side for each reactive component, a flow line (3, 4) is associated with the mixing head (2) with a Reservoir (5, 6) for the respective reactive component connects, wherein the mixing head (2) on the output side for each reactive component, a return line (7, 8) is associated with the mixing head (2) with the reservoir (5, 6) for the respective reactive component connects, wherein a spool (11) through the mixing chamber (1) translationally by three different zones (Z1, Z2, Z3) is moved, in which the flow lines and return lines and the mixing chamber are hydraulically connected or interrupted. In order to improve the processing of the reactive components, it is provided according to the invention that the control slide (11) after firing first with a first average speed (v1) from the first zone (Z1) via the second zone (Z2) in the third zone (Z3) is moved, wherein the spool (11) after reaching the third zone (Z3) is either temporarily stopped or at a second average speed (v2), which is reduced compared to the first average speed (v1) is moved before it axial Final position reached.

Description

• – durch eine erste Zone, in der die Vorlaufleitungen über die Düsen hydraulisch mit der Mischkammer verbunden sind, während die Rücklaufleitungen hydraulisch gegenüber den Vorlaufleitungen und der Mischkammer abgesperrt sind,
• – eine zweite Zone, in der die Vorlaufleitungen sowohl gegenüber der Mischkammer als auch gegenüber den Rücklaufleitungen hydraulisch abgesperrt sind, und
• – eine dritte Zone, in der die Vorlaufleitungen über die Rezirkulationsnuten hydraulisch mit den Rücklaufleitungen verbunden sind, während die Mischkammer gegenüber den Vorlaufleitungen und den Rücklaufleitungen hydraulisch abgesperrt ist.

The invention relates to a method for mixing reactive components in a mixing chamber having a mixing head, wherein the mixing head is associated with a feed line for each reactive component on the input side, which connects the mixing head with a supply reservoir for the respective reactive component, the output side of the mixing head for each reactive component associated with a return line is, which connects the mixing head with the reservoir for the respective reactive component, wherein the reactive components are first moved in liquid form in the circuit via the mixing head by each reactive component is passed from the reservoir via the flow line in the mixing head, passed from the flow line into a recirculation is, which is incorporated in a translationally movable in the mixing head in a direction of displacement spool, and from the recirculation via the return line in the reservoir to is recycled, wherein the reactive components are then injected via nozzles in the mixing chamber, wherein the mixing chamber is then mechanically cleaned by means of the spool by the spool is inserted with its one axial end into the mixing chamber, wherein the spool when translational displacement of the guide Reactive components in circulation to the final position during mechanical cleaning is guided through three different zones, namely

• By a first zone, in which the feed lines are hydraulically connected to the mixing chamber via the nozzles, while the return lines are hydraulically shut off from the feed lines and the mixing chamber,
• - A second zone in which the flow lines are hydraulically shut off both with respect to the mixing chamber and with respect to the return lines, and
• A third zone in which the supply lines are hydraulically connected to the return lines via the recirculation grooves, while the mixing chamber is hydraulically shut off from the supply lines and the return lines.

With such a method, at least two reactive plastic components can be mixed and applied. These components may be a polyurethane raw material system, but also, for example, a polyamide raw material system. Furthermore, it can be both foaming and compact systems.

The method is preferably used in the case of groove-controlled mixing heads with relatively long mixing chambers, in particular if the ratio of mixing chamber length to mixing chamber diameter is at least three.

In the case of groove-controlled mixing heads, the switching from the so-called recirculation mode to the so-called shot mode takes place by means of a control slide, into which corresponding recirculation grooves are incorporated, which in the recirculation mode hydraulically connect the respective feed line into the mixing head with the respective return line from the mixing head. In the shot mode, however, blocks the spool, the hydraulic connection between the supply and return line and are for the hydraulic connection in the mixing chamber free, in which the reactive components are mixed together and then discharged.

Mixing heads that work on this principle are known and are used, for example, in the "Plastics Handbook", Volume 7, Hanser Verlag, 2nd edition (ISBN 3-446-13614-2) on page 154 described.

The problem with such mixing heads that in the recirculation phase, a relatively long range of Rezirkulationsnuten not with the medium (ie with the material of the components to be mixed) is flowed through. At the same time this area is filled during the rapid switching of the spool from the firing position in the recirculation position with the reaction mixture, which is still after firing at the mixing chamber wall and in the so-called gatehouse of the nozzle (ie in the shot mode between the nozzle and mixing chamber and recirculation between the nozzle and spool or between the nozzle and Rezirkulationsnut).

In the time until the next shot, the reaction mixture, which is located in this non-perfused area of the recirculation, harden. The thereby forming plug can then lead to the next switching to the fact that the time of the positive coverage (ie in the time when the flow line with the return line or with the mixing chamber is hydraulically connected) significantly extended, which makes it disadvantageous to strong Pressure peaks and consequently too strong hose breathing (ie to an expansion of the tube volume as a result of the pressure peak) can occur during switching.

This can result in various adverse effects:
It may come to a shutdown of the machine due to exceeding the maximum pressure.

It can also lead to a significant shift in the mixing ratio of Reactive components come at the start of the shot due to strong hose breathing.

Finally, larger variations in shot weights can result.

The invention is therefore based on the object, a method of the type mentioned in such a way that the mentioned disadvantages are avoided. Accordingly, the pressure should be kept as free as possible of pressure peaks. Furthermore, the aim is to maintain as constant as possible a mixing ratio between the individual reactive components. The shot weights should also be kept as constant as possible.

The solution of this object is according to the invention characterized in that the spool is moved after firing first with a first average speed from the first zone on the second zone in the third zone, wherein the spool is either temporarily stopped after reaching the third zone or with a second average speed, which is reduced compared to the first average speed, is moved before it reaches its axial end position.

The second average speed is preferably at most 50% of the first average speed.

The first average speed is furthermore preferably at least 0.1 m / s. The first average speed of at least 0.1 m / s is in this case preferably maintained when passing through the second zone.

The second average speed is preferably at most 0.05 m / s.

The spool may also be stopped in the third zone for a predetermined time before reaching its axial end position, according to another embodiment of the invention; the predetermined time is preferably at least 5 seconds.

In this case, a cylindrical mixing chamber is preferably used. The mixing chamber length is preferably at least three times the mixing chamber diameter.

The mixing head used is preferably a high-pressure mixing head.

Accordingly, the invention proposes a procedure in which the aforementioned adverse effects can be avoided. The spool (control ram) is not driven at firing end at a constant high speed from one end position to the other end position. After fast passage through the zone of positive coverage, in which the flow line is connected neither to the return line nor to the mixing chamber, the speed of the control spool is then reduced (possibly to a stop) before the spool reaches its final end position for recirculation.

The spool should therefore move after firing first at high speed from the first zone on the second zone in the third zone in which it is either temporarily stopped or moves at significantly reduced speed before he reaches its front end position.

In a preferred embodiment of the method, the average speed when passing through the second zone is at least five times as high as the average speed when passing through the third zone.

Mixing heads with long mixing chambers are used, for example, in applications in which a mold has to be filled with compact reactive plastic. In this case, it is necessary to ensure a sufficiently high pressure in the mold even after firing, in order to avoid defects in the component as a result of thermal or chemical fading or as a result of expulsion from the mold. In this case, the method according to the invention makes it possible, by appropriate adaptation to the application, to control the pressure in the mold after the end of firing by repositioning material with the aid of the control tappet.

In the drawings, an embodiment of the invention is shown. Show it:

1 in radial section a mixing head with a mixing chamber, in which two reactive components are mixed together and discharged, wherein a spool is arranged in an upper end position,

2 in radial section the lower part of the mixing head 1 wherein the spool is disposed in a lower end position (cleaning position),

3 in radial section the mixing head, wherein the spool is arranged in the upper end position at the beginning of a first zone Z ₁ ,

4 the mixing head in the representation after 3 wherein the spool is located at the end of the first zone Z ₁ ,

5 the mixing head in the representation after 3 , wherein the spool is arranged in a second zone Z ₂ ,

6 the mixing head in the representation after 3 , wherein the spool valve is arranged at the beginning of a third zone Z ₃ ,

7 The mixing head in the representation after 3 , wherein the spool is located at the end of the third zone Z ₃ , and

8th the course of two velocity profiles over the displacement of the spool from the beginning of the first zone Z ₁ to the end of the third zone Z _3rd

In 1 is a mixing head 2 with a mixing chamber 1 shown in simplified form, consisting essentially of a mixing head housing 14 , a spool 11 with incorporated recirculation grooves 9 and 10 as well as with a sealing groove 15 , Nozzles 12 and 13 as well as a lid 16 for closing in the mixing head housing 14 integrated hydraulic chamber 17 ,

In the sketched sectional view and the schematically indicated connection of the mixing head 2 to the supply of two reactive components A and B are respective flow lines 3 and 4 and return line 7 and 8th to the respective storage reservoirs 5 and 6 to recognize.

The dosage of the reactive components via metering pumps 20 and 21 ,

In the illustrated view according to 1 is the mixing head 2 in Schäumposition, in which the spool 11 is positioned in its rear (upper) end position. The nozzles 12 and 13 are shown as simple apertures in this case. At the nozzles 12 . 13 Of course, it can also be about pin nozzles in which an adjustable pin in conjunction with the pinhole forms an annular gap.

As in 1 can still be seen, the mixing chamber length L is a multiple of the mixing chamber diameter D.

2 shows an enlarged view of the lower part of the mixing head 2 in recirculation position. In this illustration, it is easy to see how the supply lines 3 and 4 over the nozzles 12 and 13 , the gatekeeper holes 18 and 19 and those in the spool 11 incorporated recirculation grooves 9 and 10 hydraulically with the respective return line 7 and 8th are connected.

In the 3 to 7 are the different working zones with the associated positions of the spool 11 shown.

3 shows the mixing head 2 in the foaming position. The spool 11 is positioned in its rear (upper) end position and gives the connection of the supply lines 3 . 4 over the nozzles 12 . 13 into the mixing chamber 1 free. At the same time, the spool is blocked 11 the connection of the supply lines 3 . 4 in the return lines 7 . 8th , In the position shown is the spool 1 in a first zone Z ₁ .

After firing the spool moves 11 from its rear end position (shown in 1 and 3 ) in the direction of its front (lower) end position (shown in FIG 2 and in 7 ).

In 4 is the spool 11 also still in the first zone Z ₁ , however, in this position, the transitional region of the first zone Z ₁ begins in a second zone Z ₂ . Upon further movement down the gatehouse hole 18 . 19 partially closed.

In 5 reaches the spool 11 the second zone Z ₂ . Both the hydraulic connection from the supply lines 3 . 4 into the mixing chamber 1 as well as from the supply lines 3 . 4 in the return lines 7 . 8th is now completely through the spool 11 locked.

The second zone Z ₂ extends to the in 6 shown position of the spool 11 in which a third zone Z ₃ begins.

Upon further movement reaches the spool 11 then the transition region between the second zone Z ₂ and the third zone Z ₃ , in which the flow lines 3 . 4 over the nozzles 12 . 13 and the at least partially open porter holes 18 . 19 to the recirculation grooves 9 . 10 (Control grooves) and thus to the return lines 7 . 8th hydraulically connected.

In 6 reaches the spool 11 then finally the third zone Z ₃ . Now the hydraulic connection of the supply lines 3 . 4 to the return lines 7 . 8th over the nozzles 12 . 13 and via the recirculation grooves 9 . 10 fully unlocked.

In 7 reaches the spool 11 Finally, its lower end position, which usually corresponds to the standard recirculation position. Again, the hydraulic connection of the flow lines 3 . 4 to the return lines 7 . 8th over the nozzles 12 . 13 and via the recirculation grooves 9 . 10 fully unlocked.

It is essential that the spool 11 the area between the in 4 and 6 represented position (second zone Z ₂ ) traversed at the highest possible speed or passes through, while the speed when passing through or traversing the area between the in 6 and the in 7 shown position (third zone Z ₃ ) is then significantly reduced, the spool may even be stopped for a defined period of time, before his front end position (according to 7 ) reached.

This is again in for two possible speed gradients 8th illustrated. Here is for the translatory movement of the spool valve 11 in the displacement direction T, the extension of the three zones Z ₁ , Z ₂ and Z ₃ registered, wherein above the mixing head 2 the course of the velocity v over the path coordinate s in the direction of displacement T is sketched with reference to two examples.

In the upper curve v = v (s), it can be seen that the first two zones Z ₁ and Z ₂ (after an acceleration phase at the beginning of the first zone Z ₁ ) are traversed at a substantially constant and relatively high speed. After reaching the third zone Z ₃ , the speed v is then substantially reduced, and then at the end of the movement (shown for the spool 11 in the mixing head 1 according to 8th ) to become zero.

In the curve shown below is provided that in the zones Z ₁ and Z _{2 are the} same conditions as in the upper curve, but then the speed over a certain extent of the third zone Z _{3 is} close to zero, ie here dwells the spool 11 for a while almost at rest, before returning to the final position (in 8th at the right end of the mixing head 2 ) emotional.

Consequently, in all cases, that is the spool valve 11 After firing, first with a first average (ie, averaged over the zone) speed v ₁ from the first zone Z ₁ via the second zone Z ₂ in the third zone Z _{3 is} moved. After reaching the third zone Z ₃ , the spool 11 either temporarily stopped (see lower curve in 8th ) or it is moved on with a second average (ie, averaged over the zone) speed v ₂ through the third zone Z ₃ , which is, however, substantially reduced compared to the first average speed v ₁ .

LIST OF REFERENCE NUMBERS

1

mixing chamber

2

mixing head

3

Flow line component A

4

Flow line component B

5

Reservoir reservoir component A

6

Reservoir reservoir component B

7

Return line component A

8th

Return line component B

9

Rezirkulationsnut

10

Rezirkulationsnut

11

spool

12

jet

13

jet

14

Mixing head housing

15

sealing groove

16

cover

17

hydraulic chamber

18

Gatekeeper hole component A

19

Gatekeeper bore component B

20

Dosing pump component A

21

Dosing pump component B

A

reactive component

B

reactive component

Z ₁

first zone

Z ₂

second zone

Z ₃

third zone

v ₁

first medium speed

v ₂

second medium speed

L

Mixing chamber length

D

Mixing chamber diameter

T

displacement direction

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• "Plastics Handbook", Volume 7, Hanser Verlag, 2nd Edition (ISBN 3-446-13614-2) on page 154. [0005]

Claims (10)

Method for mixing reactive components in a mixing chamber ( 1 ) mixing head ( 2 ), wherein the mixing head ( 2 ) on the input side for each reactive component, a flow line ( 3 . 4 ) associated with the mixing head ( 2 ) with a reservoir ( 5 . 6 ) for the respective reactive component, wherein the mixing head ( 2 ) on the output side for each reactive component a return line ( 7 . 8th ) associated with the mixing head ( 2 ) with the reservoir ( 5 . 6 ) for the respective reactive component, the reactive components initially in liquid form in the circulation via the mixing head ( 2 ) by removing each reactive component from the reservoir ( 5 . 6 ) via the flow line ( 3 . 4 ) in the mixing head ( 2 ), from the supply line ( 3 . 4 ) in a recirculation groove ( 9 . 10 ), which in one in the mixing head ( 2 ) translationally in a direction of displacement (T) displaceably arranged spool ( 11 ) and of the recirculation groove ( 9 . 10 ) via the return line ( 7 . 8th ) in the reservoir ( 5 . 6 ), whereby the reactive components are subsequently passed through nozzles ( 12 . 13 ) into the mixing chamber ( 1 ), the mixing chamber ( 1 ) then by means of the control slide ( 11 ) is mechanically cleaned by the spool ( 11 ) with its one axial end into the mixing chamber ( 1 ) is inserted, wherein the spool ( 11 ) is guided during the translational displacement of the leadership of the reactive components in the circulation to the end position during mechanical cleaning through three different zones, namely - by a first zone (Z ₁ ), in which the flow lines ( 3 . 4 ) over the nozzles ( 12 . 13 ) hydraulically with the mixing chamber ( 1 ), while the return lines ( 7 . 8th ) hydraulically with respect to the flow lines ( 3 . 4 ) and the mixing chamber ( 1 ) are shut off, - a second zone (Z ₂ ), in which the flow lines ( 3 . 4 ) both opposite the mixing chamber ( 1 ) as well as with respect to the return lines ( 7 . 8th ) are hydraulically shut off, and - a third zone (Z ₃ ), in which the flow lines ( 3 . 4 ) via the recirculation grooves ( 9 . 10 ) hydraulically with the return lines ( 7 . 8th ), while the mixing chamber ( 1 ) compared to the flow lines ( 3 . 4 ) and the return lines ( 7 . 8th ) is hydraulically shut off, characterized in that the spool ( 11 ) is moved to the first zone (Z ₁ ) via the second zone (Z ₂ ) in the third zone (Z ₃ ) after firing first with a first average speed (v ₁ ), wherein the spool ( 11 ) is either temporarily stopped after reaching the third zone (Z ₃ ) or at a second average speed (v ₂ ), which is reduced compared to the first average speed (v ₁ ), is moved before it reaches its axial end position. A method according to claim 1, characterized in that the second average speed (v ₂ ) is at most 50% of the first average speed (v ₁ ). A method according to claim 1 or 2, characterized in that the first average speed (v ₁ ) is at least 0.1 m / s. A method according to claim 3, characterized in that the first average speed (v ₁ ) of at least 0.1 m / s is maintained when passing through the second zone (Z ₂ ). Method according to one of claims 1 to 4, characterized in that the second average speed (v ₂ ) is at most 0.05 m / s. Method according to one of claims 1 to 5, characterized in that the spool ( 11 ) in the third zone (Z ₃ ) is stopped for a predetermined time before reaching its axial end position. A method according to claim 6, characterized in that the predetermined time is at least 5 seconds. Method according to one of claims 1 to 7, characterized in that a cylindrical mixing chamber ( 1 ) is used. A method according to claim 8, characterized in that the mixing chamber length (L) is at least three times the mixing chamber diameter (D). Method according to one of claims 1 to 9, characterized in that as a mixing head ( 2 ) a high pressure mixing head is used.

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