GB1601699A

GB1601699A - Method and apparatus for dispersing a liquid additive throughout a plastics material

Info

Publication number: GB1601699A
Application number: GB45697/77A
Authority: GB
Original assignee: General Engineering Co Ltd
Current assignee: General Engineering Co Ltd
Priority date: 1977-11-03
Filing date: 1977-11-03
Publication date: 1981-11-04
Also published as: JPS5490260A; JPS6237659B2; FR2407811A1; DE2844753A1

Description

(54) METHOD AND APPARATUS FOR DISPERSING A LIQUID ADDITIVE THROUGHOUT A PLASTICS MATERIAL (71) We, THE GENERAL ENGINEERING Co. (RADCLIFFE) LIMITED, a British Com- pany of Station Works, Bury Road, Radcliffe, Manchester M26 9UR do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention concerns a method and apparatus for dispersing a liquid additive throughout a plastics material.

We have described in our co-pending application No. 35035/77 (Serial No.

1601698) for the grant of Letters Patent a method and apparatus whereby the simultaneous extrusion of plastics material exhibiting different characteristics can be carried out using a single extruder for a basic plastics material. In the specification of the application aforesaid we have disclosed a method of simultaneously producing, frorn a single source of basic plastics material, a product or series of products including different forms of plastics material which includes the steps of feeding a basic plastics material through a screw extruder, dividing the stream of homogenised plastics material issuing from the extruder into a plurality of separate streams, injecting a predetermined quantity of a liquid additive incorporating a plastics material modifying agent into at least one stream of basic plastics material, metering the various streams of plastics material and dispersing the modifying agent or agents throughout their respective stream or streams of basic plastics material and feeding the various streams of plastics material to extruded product forming means.

We have also disclosed an apparatus for carrying out the method aforesaid which includes a screw intruder for homogenising a basic plastics material, a means for feeding the homogenised material to a manifold to produce a plurality of individual streams, there being an additive injecting means for feeding a predetermined quantity of liquid modifying agent into at least one stream of basic plastics material and dispersing the modifying agent therethrough, and extruded product forming means for the plastics material.

We have now discovered that in some instances difficulties are experienced in ensuring that the modifying agent is completely effectively dispersed throughout the basic plastics material and thus it is an object of the present invention to provide a method and an apparatus which, while being relatively simple to control and apply is effective in use and will thus eliminate, or at least substantially eliminate the aforesaid difficulty.

Thus according to one aspect of the present invention there is provided a method of dispersing a liquid additive incorporating a plastics material modifying agent throughout a stream of basic plastics material, said method including the steps of at least partially dividing a stream of basic plastics material by means of a device used for the injection of the modifying agent, injecting the modifying agent into the partially divided stream of the basic plastics material thus to cause initial dispersive mixing of the basic plastics material and the modifying agent and thereafter subjecting the dispersively mixed mass to shearing action in a homogenising device to cause final dispersion of the modifying agent throughout the basic plastics material.

According to a further aspect of the present invention an apparatus for carrying out the method aforesaid includes the provision of a plastics material modifying agent dispersing means in a basic plastics material supply line, said dispersing means including a device for at least partially dividing a single stream of basic plastics material for the reception of the modifying agent, and further dispersing means in the supply line for further dispersing the modifying agent in the basic plastics material.

Conveniently the device for at least partially dividing the stream of basic plastics material includes means projecting into the supply line in the form of a plurality of spaced-apart hollow injector probes.

The invention will now be described fur ther, by way of example, with reference to several practical forms thereof and the accompanying drawings in which: FIG. 1 is a diagrammatic sectional elevation of one form of dispersing means made in accordance with the invention, parts being omitted for clarity.

FIG. 2 is a section on the line II-II of FIG. 1 the parts omitted from FIG. 1 being included.

FIG. 3 is an enlarged sectional view on the line III-III of FIG. 1.

FIG. 4 is a diagrammatic section showing the dispersively mixed material which issues from the dispersing means shown in FIGS. 1 to 3.

FIG. 5 is a view similar to FIG. 1 of a modification.

FIG. 6 is a view similar to FIG. 2 of the modification of FIG. 5.

FIGS. 7 and 8 are views of two possible variations of dispersively mixed material obtainable from the device of FIGS. 5 and 6.

FIG. 9 is a view similar to FIG. 1 of a still further modification.

FIG. 10 is a view similar to FIG. 2 of the device illustrated in FIG. 9 and FIGS. 11 and 12 are views similar to FIGS. 7 and 8 showing possible variations of the products which can be produced using the device of FIGS. 9 and 10.

Injector means for achieving initial dispersive mixing of a homogenised basic plastics material and a modifying agent which modifies the physical properties of the plastics material will be described. In the description reference will thus be made to the injection of a colouring pigment, but it should be borne in mind that the injecting means can be used for the dispersive mixing of a basic plastics material with a modifying agent, which, for example, can be used to modify the chemical properties of the basic plastics material, or, in fact, the physical and the chemical properties.

Thus an injector means made in accordance with the form of the invention shown in FIGS. 1, 2 and 3 comprises a body 10 which is conveniently of open-ended cylindrical form and is provided with external screw threads 11 at each of the open ends thereof. The body 10 can thus be incorporated in a supply line (not shown) for the basic plastics material. The passage 12 through the body 10 is conveniently of the same diameter as the internal diameter of the supply line into which it is secured. At 1200 spacing around the body 10 (see FIG.

2) and intermediate its ends, there are provided internally projecting hollow probes 13, these being secured to the body 10 by providing screw threaded ends 14 (see FIG.

1) thereon which screw into drilled and tapped radially disposed holes in the wall of the body 10. Conveniently externally of the body 10 is provided a manifold 15 (shown by dotted lines in FIG. 2) or other means to which are connected the three radially disposed probes 13. A means such as a pump (not shown) for the introduction of colouring pigment into the probes is connected to the manifold 15 by a supply line 16. If desired each of the probes could be supplied with pigment from a separate source in which case there would be a pump for each probe.

As can be seen from FIG. 3 the probe 13 may be provided with a core 17 for the purpose of restricting the cross-sectional area of the bore of the probes. The crosssectional area of the core 17 is so chosen that the annular space formed for the passage therethrough of the colouring pigment is of such a size that the tendency of the plastics material, which in use flows through the passage 12 of the body 10, to flow into the annular space in the probes in a direction counter to the flow of colouring pigment is substantially wholly prevented.

The injector means is, in use, located downstream of a homogenising means for the basic plastics material (for example a screw extruder) and upstream of a homogenising means for the final dispersion of the initially dispersively mixed modifying agent throughout the basic plastics material (conveniently the latter homogenising means is a gear pump).

In use, a stream of basic plastics material flowing along the supply line in the direction of the arrow A is partially divided as it passes through the cylindrical injector means by virtue of inwardly projecting hollow probes 13 which extend from the internal wall of the body 10 towards the axial centre line thereof. Colouring pigment is pumped to and through the probes and is thus dispersed onto the internal surfaces 18 (see FIG. 4) created in the basic plastics material 19 in the region of the downstream side of the probes 13. The colouring pigment is thus dispersively mixed with the basic plastics material not only due to the fact that it is pumped onto the internal surfaces but also due to the fact that some at least of the modifying agent tends to migrate as shown at 20 at least partially around the outer surface of the basic plastics material 19 between it and the internal wall of the injector body 10. The thus dispersively mixed materials pass from the injector and along the supply line downstream of the injector into the final mixing and homogenising device in which the additive is dispersed throughout the stream of basic plastics material. As stated above, the final mixing and homogenising device is conveniently a gear pump.

While reference has been made above to the provision of an injector having three probes 13 spaced at 120 around the internal periphery of the body of the injector, many modifications of the injector are pos sible. For example, the probes may be more or less than three in number and they may be disposed in the body at spacing other than 120 . In its simplest form, the injector is provided with a single probe.

It is also possible to provide a greater degree of dispersive mixing than that achieved by the device illustrated in FIGS. 1, 2 and 3. To achieve this divisions are provided in the body 10 in an axial direction. One possible arrangement is shown in FIGS. 5 and 6. Conveniently two divisions 21 are provided thus to form three separate passageways 22 through the body 10 of the injector. Conveniently there is a probe 13 in each passageway 22. The probes are connected via connectors 23 to either a manifold (not shown) or to separate pumps.

Clearly more than three separate passageways 22 can be provided if desired and in the case in which a larger number of passageways is provided it may be found advantageous to provide a probe for each passage. Alternatively some passageways may exist without a probe therein. In arrangements of the kind just referred to it is found that the modifyiing agent tends not only to flow onto the internal surfaces created by dividing the basic plastics material by the presence of the probes but also to tend to flow onto the internal surfaces of the basic plastics material created by the divisions 21 in the bore of the body.

FIGs. 7 and 8 illustrate the effects just mentioned; FIG. 7 shows the form of material which can be produced when there is only one probe 13. The form of material produced when there is a probe in each passage is shown in FIG. 8.

Thus due to the degree of dispersive mixing achieved it is possible subsequently more easily further to disperse the colouring pigment throughout the basic plastics material in the final mixing and homgenising device.

It is possible to arrange for the additive injection means to be incorporated into the divisions, in which case they, in effect become the probes. In such an arrangement the modifying agent could conveniently be ejected from the downstream end of the divisions or at a position intermediate the ends thereof. A possible arrangement for introducing the additive intermediate the ends of the divisions is shown in FIGS. 9 and 10.

Thus in the arrangement illustrated there is provided an initial dispersing device having a two part body. The two parts 24 and 25 are adapted to fit closely together in the plane transverse to the flow direction of the plastics material within each body part is a pair of divisions 26, 27 which when the body parts are assembled collectively pro vide three channels 28 which lie axially of the body. The face of one part (say part 25) is relieved as at 29 around the central channel 28, as shown in FIG. 10 in partic ular and the body part 25 is provided with a supply passage 30 which at one end is enlarged and provided with a connector for a supply pipe (not shown) for the additive.

At the other end the passage terminates in the relief 29. The axial gap formed by the relief 29 is so chosen that any tendency for the basic plastics material to flow into the relief 29 counter to the flow direction of the colouring pigment is substantially wholly prevented. As shown in FIG. 10 by the broken line 31 the relief can be large enough to encompass the three (or other number) of channels 28 formed in the de vice.

Conveniently the two parts of the body are flanged and securing bolts 32 are used to hold the parts together.

FIG. 11 illustrates the form of initial dispersive mixing achieved when the relief encompasses only the central channel 28 of the device. FIG. 12 on the other hand shows the initial dispersive mixing achieved when all of the channels are encompassed by the relief.

When the relief encompasses all of the channels the resistance to flow of the liquid additive is reduced.

It should be borne in mind that when the apparatus is being used it is necessary initially to commence pumping the modi fying agent into the device to prevent block age of the probes or the relief due to the tendency of the basic plastics material to enter the supply passages for the additive and thus constrict or prevent the flow of modifying agent into the mass of basic plastics material flowing through the injec tor.

It is possible somewhat to reduce the risk of basic plastics material flowing into the probes by inclining them in the direction of the flow of the basic plastics material or by providing probes having an end region which lies parallel to the axis of the body, as, for example is the case when there are provided divisions incorporating additive flow channels as described above.

WHAT WE CLAIM IS:- 1. A method of dispersing a liquid addi tive incorporating a plastics material modi fying agent throughout a stream of basic plastics material, said method including the steps of at least partially dividing a stream

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

While reference has been made above to the provision of an injector having three probes 13 spaced at 120 around the internal periphery of the body of the injector, many modifications of the injector are pos sible. For example, the probes may be more or less than three in number and they may be disposed in the body at spacing other than 120 . In its simplest form, the injector is provided with a single probe.

It is also possible to provide a greater degree of dispersive mixing than that achieved by the device illustrated in FIGS. 1, 2 and 3. To achieve this divisions are provided in the body 10 in an axial direction. One possible arrangement is shown in FIGS. 5 and 6. Conveniently two divisions 21 are provided thus to form three separate passageways 22 through the body 10 of the injector. Conveniently there is a probe 13 in each passageway 22. The probes are connected via connectors 23 to either a manifold (not shown) or to separate pumps.

Clearly more than three separate passageways 22 can be provided if desired and in the case in which a larger number of passageways is provided it may be found advantageous to provide a probe for each passage. Alternatively some passageways may exist without a probe therein. In arrangements of the kind just referred to it is found that the modifyiing agent tends not only to flow onto the internal surfaces created by dividing the basic plastics material by the presence of the probes but also to tend to flow onto the internal surfaces of the basic plastics material created by the divisions 21 in the bore of the body.

FIGs. 7 and 8 illustrate the effects just mentioned; FIG. 7 shows the form of material which can be produced when there is only one probe 13. The form of material produced when there is a probe in each passage is shown in FIG. 8.

Thus due to the degree of dispersive mixing achieved it is possible subsequently more easily further to disperse the colouring pigment throughout the basic plastics material in the final mixing and homgenising device.

It is possible to arrange for the additive injection means to be incorporated into the divisions, in which case they, in effect become the probes. In such an arrangement the modifying agent could conveniently be ejected from the downstream end of the divisions or at a position intermediate the ends thereof. A possible arrangement for introducing the additive intermediate the ends of the divisions is shown in FIGS. 9 and 10.

Thus in the arrangement illustrated there is provided an initial dispersing device having a two part body. The two parts 24 and

25 are adapted to fit closely together in the plane transverse to the flow direction of the plastics material within each body part is a pair of divisions 26, 27 which when the body parts are assembled collectively pro vide three channels 28 which lie axially of the body. The face of one part (say part 25) is relieved as at 29 around the central channel 28, as shown in FIG. 10 in partic ular and the body part 25 is provided with a supply passage 30 which at one end is enlarged and provided with a connector for a supply pipe (not shown) for the additive.

At the other end the passage terminates in the relief 29. The axial gap formed by the relief 29 is so chosen that any tendency for the basic plastics material to flow into the relief 29 counter to the flow direction of the colouring pigment is substantially wholly prevented. As shown in FIG. 10 by the broken line 31 the relief can be large enough to encompass the three (or other number) of channels 28 formed in the de vice.

Conveniently the two parts of the body are flanged and securing bolts 32 are used to hold the parts together.

FIG. 11 illustrates the form of initial dispersive mixing achieved when the relief encompasses only the central channel 28 of the device. FIG. 12 on the other hand shows the initial dispersive mixing achieved when all of the channels are encompassed by the relief.

When the relief encompasses all of the channels the resistance to flow of the liquid additive is reduced.

It should be borne in mind that when the apparatus is being used it is necessary initially to commence pumping the modi fying agent into the device to prevent block age of the probes or the relief due to the tendency of the basic plastics material to enter the supply passages for the additive and thus constrict or prevent the flow of modifying agent into the mass of basic plastics material flowing through the injec tor.

It is possible somewhat to reduce the risk of basic plastics material flowing into the probes by inclining them in the direction of the flow of the basic plastics material or by providing probes having an end region which lies parallel to the axis of the body, as, for example is the case when there are provided divisions incorporating additive flow channels as described above.

WHAT WE CLAIM IS:- 1. A method of dispersing a liquid addi tive incorporating a plastics material modi fying agent throughout a stream of basic plastics material, said method including the steps of at least partially dividing a stream

of basic plastics material by means of a device used for the injection of the modifying agent, injecting the modifying agent into the partially divided stream of the basic plastics material thus to cause initial dispersive mixing of the basic plastics material and the modifying agent and thereafter subjecting the dispersively mixed mass to shearing action in a homogenising device to cause final dispersion of the modifying agent throughout the basic plastics material.
2. A method as claimed in Claim 1 including the step of injecting the modifying agent by passing same through a hollow probe adapted partially to divide the stream of basic plastics material.
3. A method as claimed in Claim 1 or 2 including the step of partially dividing the stream of basic plastics material by means of a plurality of hollow probes and pumping modifying agent through a manifold common to at least two of the probes.
4. A method as claimed in Claim 1 including the step of dividing a stream of basic plastics material into at least two discrete streams and injecting the modifying agent into one at least of said discrete streams by means of a hollow probe which additionally serves at least partially to divide said at least one discrete stream of basic plastics material.
5. A method as claimed in Claim 1 including the step of dividing a stream of basic plastics material into at least two discrete streams and passing the modifying agent into the means for dividing the stream of basic plastics material thereby to inject the modifying agent into the basic plastics material at some at least of the positions at which the latter is divided.
6. A method as claimed in Claim 4 including the step of recombining the discrete streams of basic plastics after injecting the said modifying agent into at least one of the said discrete streams.
7. A method as claimed in Claim 5 including the step of recombining the said discrete streams of'basic plastics material after injecting the modifying agent at some at least of the positions at which the basic plastics material is divided.
8. Apparatus for carrying out the method claimed in Claim 1 including a plastics material modifying agent dispersing means in a basic plastics material supply line, said dispersing means including a device for at least partially dividing a single stream of basic plastics material for the reception of the modifying agent, and further dispersing means in the supply line for further dispersing the modifying agent in the basic plastics material.
9. Apparatus as claimed in Claim 8 including a tubular element adapted to be located in a basic plastics material supply line, hollow probe means projecting into said tubular element, adapted at least partially to divide said stream of basic plastics material and means for supplying a modifying agent to said probe means.
10. Apparatus as claimed in Claims 8 or 9 including a plurality of dispersing means for supplying a modifying agent and for at least partially dividing said stream of basic plastics material, said dispersing means being spaced-apart in said tubular element and being each connected to a means for supplying modifying agent thereto.
11. Apparatus as claimed in Claim 10 in which there is provided a manifold surrounding at least part of the tubular element and being in communication with at least some of a plurality of means for at least partially dividing a stream of basic plastics material, said manifold being provided with means whereby it can be connected to pump means for supplying said modifying agent.
12. Apparatus as claimed in Claim 10 or 11 in which the means for at least partially dividing said stream of basic plastics material comprises a plurality of spacedapart hollow probes projecting radially inwardly into the bore of said tubular element and terminating at a position spaced from the axial centreline thereof.
13. Apparatus as claimed in Claim 8 in which there is provided a dispersing means including a body adapted to be located in a basic plastics material supply line, said body portion having a plurality of separate passageways therethrough whereby a single stream of basic plastics material may be separated into a plurality of discrete streams, there being hollow probe means within the body and projecting into at least one of the passageways and adapted to at least partially divide plastics material passing therethrough and to inject modifying agent.
14. Apparatus as claimed in Claim 13 in which there is a hollow probe means projecting into each of the separate passageways of the body, there being means for supplying modifying agent to each of the hollow probes.
15. Apparatus as claimed in Claim 14 in which the means for supplying modifying agent to the probes is common to all of the probes.
16. Apparatus as claimed in Claim 8 in which there is provided a dispersing means including a body adapted to be located in a basic plastics material supply line, said body having a plurality of separate passageways therethrough whereby a single stream of basic plastics material may be separated into a plurality of discrete streams, at least one of the divisions in the body separating one passageway from adjacent passageways being provided with a bore through which modifying agent may pass to an outlet whereby it can disperse and become injected into the division between at least two of the discrete streams of basic plastics material.
17. Apparatus as claimed in Claim 16 in which the body is in two parts having mating surfaces located in a plane transverse to the longitudinal axes of aligned separate passageways therethrough, there being a bore in one part of the body through which modifying agent may pass to a relief formed on one of the mating surfaces, said relief being of such a size as to extend wholly around one at least of the peripheries of the separate passageways whereby modifying agent may'be injected into the divisions between at least two of the discrete streams of basic plastics material.
18. Apparatus as claimed in Claim 17 in which the relief is formed on the mating surface of that part of the two part body in which the bore is formed, the said relief extending around the periphery of all of the passageways whereby modifying agent may be injected into all of the divisions of the basic plastics material.
19. Apparatus as claimed in any one of Claims 9, 10, 12, 13, 14 or 15 in which each hollow probe is provided with a core to reduce its cross-sectional area and thereby, in use, substantially reduce the tendency of the flow of basic plastics material into the probe.
20. Apparatus as claimed in Claim 17 or 18 in which the relief is of such depth as to substantially reduce the tendency of the basic plastics material to flow into the bore of the body through which the modifying agent is passed.
21. The method of injecting a liquid additive incorporating a plastics material modifying agent into a stream of basic plastics material substantially as hereinbefore described with reference to and as illustrated in Figs. 1, 2 and 3 or Figs. 5 and 6 or Figs. 9 and 10 of the accompanying draw ings.
22. Apparatus for injecting a liquid additive incorporating a plastics material modifying agent into a stream of basic plastics material substantially as hereinbefore described with reference to and as illustrated in Figs. 1, 2 and 3 or Figs. 5 and 6 or Figs. 9 and 10 of the accompanying drawings.