Patent Application
20050017412
The invention relates to methods and devices for the rapid preparation of homogenous or semi-homogenous mixtures of multi-component systems, particularly of different plastics mixtures, and for preparing and possibly also for handling and testing mouldings produced from such mixtures.
The preparation of mouldings from various plastics mixtures is, for example, important in the development of optimised plastic compositions, in the development of novel blend systems or for testing the properties of new additives in a plastic matrix. To this end in many cases series of experiments have to be carried out with numerous plastics mixtures the composition of which is changed stepwise, for example to determine the influence of changing quantities of a component on the properties of the mixtures and mouldings obtained.
Such experiments have so far been carried out in a comparably slow and little economic way, for example by mixing the plastic components with the aid of a mixer device, for example a kneader or extruder, and then moulding them, usually in the form of a granulate, in plastic injection moulding machines in a separate step. The mouldings are then tested in a following step, for example with respect to their mechanical and thermal characteristics as well as other technically relevant properties. The determination of said characteristics is laid down in various test standards; the data obtained using, for example, the DIN standards can then immediately be compared to each other.
The problem arising in connection with the described procedure comprising said separate, not integrated, independent steps is mainly the time required for the preparation of the individual plastics mixtures, for moulding the mixtures, for example in injection moulding machines, and for testing the produced mouldings in testing machines. Another disadvantage is that a long dwell time of the respective plastics mixture is required due to the back-mixing occurring in the commonly used mixers, like, for example, double screw extruders or kneaders. This results in a relatively high expenditure of time for rinsing the device and changing the mixtures. According to this method, correspondingly, only a few thousand mixtures a year can be prepared and tested per technical unit comprising the compounding unit, an injection moulding machine and testing equipment. Therefore only a small selection of the possible formulas could be prepared and tested so far while, among other proposals, efforts were made to develop the unexamined mixture ranges theoretically by interpolation of the measured values using various methods of statistical experiment design.
There are, however, questions the answers to which require considerably more plastics mixtures to be prepared, processed to mouldings and tested. For example in case of a combination of two to three plastic materials with two to three additives from which mouldings are to be formed while the composition is varied in steps of approximately one percent with respect to all components, the conventional method is unsuitable for providing the desired results within a sufficiently short period of time.
From patent literature numerous devices are known the object of which is only the preparation of mixtures of plastic materials.
In the DE 196 53 099 a device is described in which at least two plastic components are introduced into a mechanically driven mixer element, mixed in it and then conveyed into an injection moulding tool to obtain a thorough mixture of the materials processed.
In the DE 198 08 620 a device extended as compared to the DE 196 53 099 is described which includes additional storage elements comprised of a cylinder with a piston to enable the use of reactive components without the conveyor means being blocked. The metering of the stored components is also effected into the mixer element. The utilisation of a mechanically driven, rotating mixer device has the disadvantage that either the change from one composition of the mixture to the next takes a long time since a large amount of the new mixture must be continuously fed through the mixer device for rinsing or the mixer device needs to be dismounted for each change of the composition to be replaced by a cleaned one. Such devices are therefore unsuitable for rapidly changing plastics mixtures.
The EP 0 904 927 A1 describes means for introducing a reactive system composed of at least two components, particularly liquid silicone rubber, into a mould, the components being supplied to a mixer means by a volumetric metering unit comprising a metering piston and the obtained mixture being conveyed into an injection cylinder. In this case the metering unit is integrated in the injection moulding machine. It is essential in this known device that a metering unit comprising a metering piston is provided for each component and that the combination of the flows of the components is carried out in a dynamic mixer. The problem of the rapid production of mouldings having different compositions is not mentioned in said document. The EP 0 904 927 further particularly refers to reactive liquid silicone mixtures radically differing from thermoplastics in their rheologic and thermodynamic properties.
From the U.S. Pat. No. 5,688,462 an injection moulding process is known in which a static mixer is used. The mixer is disposed inside the tool directly upstream of the mould inlet to avoid a thermally induced inhomogeneity of the smelt. A rapid change of products is impossible with said device due to the missing metering and supply means.
From the DE 2 329 966 a device for preparing products of thermoplastics is known in which a static mixer at the inlet of which a second component is introduced is connected to a plasticizer, for example a screw extruder. Said device is substantially an extruder comprising a mixer means and not an injection moulding machine which, on the other hand, is required for an integrated production of mouldings.
From the U.S. Pat. No. 4,255,367 a method for preparing injection moulded products is known in which additives are introduced into the smelt flow in the flow direction between the injection means comprising a storage cylinder including a piston and the mixer element during the injection of the molten plastic. Due to the zoned addition of additives an intentionally inhomogenous moulding having a kind of core/shell structure is prepared. Such a method is, for example, absolutely unsuitable for the development of formulas in which particularly a uniform composition of the specimen is essential.
In the DE 19 902 990 a method and an apparatus are described in which a plastic material and an additive are rough mixed in a screw push plasticizer unit, mixed in a dynamic mixer and then injected into the cavity of an injection moulding tool. A drawback here is that the mixing process is very slow in such plasticizer units having a mixing effect; in addition the cleaning procedures are considerable in case of a screw push plasticizer unit so that the period of time required for the mixing and injecting process including the cleaning cycles in case of a change of the mixtures may be in a range of up to several hours.
Similar problems occurring in connection with the rapid preparation of homogenous mixtures having changing compositions are, for example, also encountered in the development of cosmetic compositions or in food technology, e.g. in the development of snack food compositions from pastes or pastry on the basis of starchy products with varying additives or changing compositions.
It is an object of the invention to provide methods and devices for the, as compared to the state of the art, considerably faster and more economic preparation of homogenous or semi-homogenous mixtures from viscous or pasty multi-component systems, particularly from various plastic systems, and for preparing and possibly for handling and testing mouldings made from such mixtures in which an easy and rapid change of the composition is possible, preferably while minimising the material consumption.
Further it should be possible to subject the mixtures or mouldings obtained to one or more tests after their preparation, particularly within the framework of an overall process comprising the preparation of mixtures and/or mouldings and the testing of the mixtures or mouldings, alternatively after their intermediate storage or in a process-linked manner.
The object is solved by the features of the independent claims. The dependent claims relate to preferred embodiments of the concept of the invention.
Plastics mixtures for the preparation of mouldings are generally homogenous, while mixtures may only be semi-homogenous, i.e. not ideally homogenous, in case of blends, the homogeneity, however, being sufficient for the production and testing of mouldings.
According to the method of the invention for the rapid preparation of homogenous or semi-homogenous mixtures having given and, in particular, frequently changing compositions and possibly of mouldings produced therefrom multi-component systems are used which comprise two or more viscous or pasty fluids (component system A) or one or more viscous or pasty fluids and one or more additives (component system B). The mixture is obtained by introducing predetermined quantity ratios of the components of the component system A or B into a rough mixer means such as, for example, an injection unit, in which the viscous or pasty state of the component system remains unchanged. The component system obtained in the rough mixer is mixed in a mixer means to obtain a homogenous or semi-homogenous mixture from which then mouldings can be prepared.
In its most general form the method according to the invention for the rapid preparation of homogenous or semi-homogenous mixtures having predetermined compositions of component systems
The primary flow may, correspondingly, consist of a plurality of components and be a rough mixture itself.
The process step III may preferably be followed by the following process step IV:
In process step II the introduction of the secondary flows into the primary flow or the establishment of a contact between the two flows creates a rough mixture structure which can be illustrated by comparison with a strand of tooth paste with coloured stripes on the circumference, the primary flow corresponding to the strand of tooth paste and the secondary flows to the coloured stripes. Each volume element (disk) extending across the cross section of said rough mixture structure already has a substantially uniform composition in the axial direction; in the radial direction, however, only little or no homogeneity exists depending on the relative quantity ratios of the components. In the downstream mixer device having a radial mixing effect the rough mixture is radially homogenised.
During the radial mixing process therefore the “tooth paste stripes” will vanish and an all over three-dimensionally homogenous or semi-homogenous mixture will be formed from which mouldings can be produced.
In the method according to the invention the flow direction advantageously remains the unchanged throughout the process steps I, II and III as well as the process step IV, if it is carried out.
This method for preparing a mixture can be carried out continuously.
If a moulding production follows as process step IV the method generally becomes altogether discontinuous unless the moulding production is a continuous extrusion.
However, the method can be carried out continuously up to the preparation of the mixtures in the process steps II or II. Further devices for an intermediate storage or buffering of a continuously generated mixture flow which enable the discontinuous production of mouldings from a continuously arriving mixture flow, e.g. by injection moulding, are known to those skilled in the art.
It may, however, be advantageous to effect a supply of the rough mixture flow by the mixer means in a flow direction opposed to the flow direction of the primary flow in process step I and the rough mixture flow in process step II in process step III and possibly also in process step IV.
Said method is discontinuous due to the reversal of the flow direction.
If such a method is used the components of the component system are introduced, in predetermined quantity ratios, into an injection unit in which the viscous or pasty state of the component system remains unchanged, homogenised or semi-homogenised in a downstream mixer device, after which mouldings can be produced from the mixture. This basic method is known from the document DE 19 902 990 mentioned above.
A first embodiment of the method according to the invention including a reversal of the flow direction in process step III and possibly also IV has the following features:
The production of mouldings may follow.
In a second embodiment of the method according to the invention including a reversal of the flow direction the introduction of the components of the component system into the cylinder of the injection unit is effected above the piston while at the same time the piston is returned from its upper stroke position to a lower stroke position and a rough mixture of the components of the component system is formed the composition of which corresponds to the predetermined overall composition, after which the rough mixture is homogenised in a mixer means having a radial and an axial mixing effect. Such a mixer means may be a dynamic mixer means, it is however, preferably a static mixer.
According to the first of these embodiments the components of the component system are introduced into one and the same volume element on the outlet side end of the cylinder when the piston is returned, preferably through inlets in the cylinder which are disposed on the same axial level.
In this case the piston may be pressed into the lower stroke position by the pressure building up due to the introduction of the components above the piston. This process can also be supported by an active retraction of the piston by its drive unit.
By introducing the components on preferably approximately the same axial level of the cylinder a rough mixture structure which again may be illustrated by comparison with a strand of tooth paste having coloured stripes is formed when the piston is retracted.
According to the above-mentioned second embodiment of the method of the invention including a reversal of the flow directions the components of the component system do not imperatively need to be introduced into the cylinder in the same volume element or on approximately the same axial level. The axial position of the inlets of the cylinder may therefore be principally different for the different components introduced since the rough mixture formed is in this case homogenised or semi-homogenised by the mixer means having an axial and a radial mixing effect.
According to this embodiment of the method of the invention it may be advantageous to introduce one or more components of the component system into the cylinder on different axial levels, particularly for reasons of space, if the corresponding supply means, valves, metering means, etc. or their ports on the cylinder are bulky and require a lot of space or if a star shaped radial arrangement, seen in the axial direction, of said means on the cylinder is to be avoided.
According to both methods including a reversal of the flow direction the homogenisation of the component system is effected by moving the piston forward so that the content of the cylinder is pressed through the mixer means.
If a moulding tool is connected, filling is advantageously effected through a nozzle formed with or without a hot channel. The downstream moulding tool is preferably an injection moulding tool, again with or without a hot channel, and advantageously comprises more than one cavity to enable the production of a plurality of mouldings, possibly in different shapes.
Preferably the secondary flows are generally introduced into the primary flow in the radial direction.
According to the method of the invention preferably at least one of the viscous or pasty fluids is molten plastic, for example a plastomer or a thermoplastic elastomer or another conveyable plastic material advantageously forming a polymer matrix. The components, however, may also be suitable for the production of polymer blends, cosmetic products (e.g. lipsticks, skin cream, etc.) or pharmaceutical products (e.g. suppositories), or they may be food components, particularly for pastry (e.g. bread, cake) or components for the production of toys (e.g. plasticine).
The mixture obtained after process step III or possibly after a following process step IV may be subjected to a reaction in a reactor or a reaction section. An advantageous application of this method is the cooking extrusion of starch-containing milled grain products which is particularly used for the production of instant flour, instant semolina or snack food. The mouldings may, in this case, be flour, semolina or snack products. The cooking extruder may here also have the function of a mixer means which, in this case, has a radial and an axial mixing effect.
According to the method of the invention preferably at least one of the components of the component system is a matrix material, particularly a molten plastic material, and at least one of the other components is an additive. Typical additives are, for example, fillers, UV stabilisers, oxidation stabilisers, catalysers, flow and demoulding agents, lubricants, polymer components, flame-retardants, colouring agents, pigments, reactive components, etc. of which one or more components are preferably introduced into the primary flow with one or more of the mentioned viscous or pasty fluids which are preferably present in the form of e.g. liquids, solutions, dispersions, emulsions, powders, granulates, smelts or fibres. Practically one or more of the components mentioned above are used for the primary flow and/or the secondary flow in rough mixed form, particularly as pre-blends.
The rough mixer means or the cylinder is preferably formed so that, depending on the requirements, a changing number of supply means for secondary flows may be connected to it by exchangeable connections, e.g. bayonet couplings. Depending on the requirements different types of supply means, like, for example, single or double screw extruders, may be connectable to the rough mixer means.
In the method according to the invention therefore principally any number of secondary flows may be selectively introduced into the primary flow.
In to a particularly preferred embodiment of the method one or more mixtures are introduced into the primary flow as secondary flows which are themselves obtained after the process step II or the process step III according to the method of the invention. Using this method particularly many potential mixture combinations and particularly homogenous final mixtures or mouldings of a particularly high quality can be obtained.
The method according to the invention is advantageously carried out in a closed system, particularly the process steps I to III or I to IV.
In this case, it is generally advantageous if one, several or all introducing means for secondary flows or supply means comprise a metering means by means of which the corresponding components of the component system may be metered in while being introduced into the cylinder to enable the setting of absolute quantities or predetermined quantity ratios of the components. The components of the component system are preferably introduced into the cylinder in the radial direction.
In case of a discontinuous method the volume of the supply means and/or the rough mixer means used for moulding in the production of mouldings or the stroke volume of the cylinder of the injection unit is preferably selected so that it corresponds to one or more fillings of the moulding tool which may have a plurality of identical or differing cavities in a per se known manner. In addition it is particularly advantageous that the devices used have as little dead volume as possible, i.e. that, if possible, the total content of the devices can be used for the preparation of mixtures or mouldings, except for the dead volume of the mixer means and the moulding tool.
The preparation of the moulding or the mouldings is advantageously carried out in a paced manner, wherein
In case of shaping by injection moulding the process step III and possibly the process step IV as well are preferably carried out with a higher mass or volume speed or with a higher throughput than the process steps I and II.
If the composition of the of the component system is changed or another component system is to be used, the dead volume of the cylinder and the mixer means and possibly also a nozzle used for moulding or the moulding tool need to be rinsed with a component system having another composition after one or more cycles of the production of mouldings from the one component system. The component system used for rinsing may then also be used to produce mouldings. In this way residues of a previous composition will be rapidly removed from the system.
According to another embodiment e.g. cylindrical or rectangular strands or foil ribbons are formed by continuous extruding of the homogenised or semi-homogenised component system, from which then the actual shaped bodies can be punched or cut.
With the method according to the invention described above preferably mouldings are prepared which serve as specimen for the determination of material-specific properties, i.e. of characteristics of the respective component system to be tested, e.g. of plastics mixtures. The method according to the invention, however, is of course also suitable as a production method for mixtures or mouldings.
The method according to the invention is preferably carried out by controlling the throughput of the primary flow and the throughputs of the secondary flows by means of a control means. This is preferably carried out so that the introduction and supply of one, several or all components of the component system is controlled depending on the type, the metered in amount and/or the metering rate. This also applies to the modified method including a reversal of the flow direction. Furthermore the production of mouldings from the obtained mixtures is preferably controlled as well.
The method according to the invention can preferably also be consolidated method comprising the production as well as the handling and testing of mouldings. In this case one or more of the following steps are carried out after process step IV:
The consolidated method is preferably integrated into one single process comprising the preparation of mouldings as well as handling and testing the mouldings and preferably also the recording and processing of the test results.
One or several or all steps of the method according to the invention including the consolidated method described above are preferably carried out or controlled using central data collection and processing, particularly using a computer system or a micro processor system. The control may also be effected using programmable logic control.
In this way, for example one or several or all conveying operations, particularly in steps (a), (b) and/or (d), are controlled by one control means. The same applies to the tests in step (c); said tests and/or the collecting, processing and/or transfer and/or output of test results are preferably also controlled by one controller.
An advantageous embodiment of the above consolidated method is characterised by the collection, processing and/or transfer of test results in or after step (c).
When the mouldings are moved to a plurality of testing means in step (b) the transportation may be effected sequentially and/or in parallel. The same applies to the tests in step (c).
In general the specific moulding type provided for the respective test is to be supplied to the various testing means.
Here either an automatic or a manual exchange of the moulding tool or the use of a moulding tool having several cavities corresponding to the mouldings to be prepared is required for the production of the mouldings; a central control of the partial processes or of the complete process being particularly suitable for such cases.
When the tests mentioned above are carried out, the mouldings are tested for one or more of their chemical, particularly their polymer chemical, physical, biochemical, biological, pharmacological, organoleptic, haptic or other relevant properties. The test may, however, also relate to one or more of the mechanical, polymer physical, optic, electric or magnetic properties.
Another aspect of the present invention is the allocation of test results to the composition of the tested mouldings. Within the scope of the invention said allocation is preferably also carried out by a control means or a data processing device.
If the allocation can be effected in a simple and univalent manner, particularly in case of test series including a small number of different mouldings or specimen, a mathematical correlation is usually not required.
However, if a large number of mouldings having different compositions are produced within relatively short periods of time in the range of minutes to hours and one or more of their properties are to be tested large amounts of data are to be handled from which the influence of the varying variables and the parameters respectively kept constant on the test results can no longer determined or derived in a simple and univalent manner in many cases. That holds true particularly for the production of plastic mouldings since here numerous combinations of process variables and process parameters are feasible and frequently need to be implemented in practise.
For such cases the scope of the invention provides for the utilisation of mathematical correlation methods and preferably for their implementation in a control means or data processing device which results in a correlation between the process variables, process parameters and moulding compositions on the one hand and one or more properties of the mouldings on the other.
Typical process variables or process parameters, i.e. values which are varied or kept constant, are, for example, the composition of the component system used, the quantity rations of the components, the processing temperatures, the type and speed of the homogenisation, the duration of the storage of specimen before the test, the heating and cooling time, the duration of rinsing operations and the quantities of the subsequent component system used therefore, etc.
Apart from various statistical evaluations a preferred method is the determination of such correlations with the aid of a neural network. Such evaluation and correlation methods are per se known to those skilled in the art so that they do not need to be discussed in detail.
With such evaluation systems trends relating to product properties can be identified even in series experiments within a relatively short period of time as compared to conventional methods.
The invention further relates to a device for the rapid preparation of homogenous or quasi-homogenous mixtures having a predetermined composition of component systems
For the preparation of mouldings the device may further include a moulding tool connected or connectable to the output of the mixer means.
According to one embodiment the device is characterised in that
In this device the conveying means of the rough mixer means substantially consists of a piston disposed in a cylinder provided therein and a piston drive (injection unit), the inlets for the secondary flows being positioned on the outlet side end of the cylinder opening into a volume element VE, the piston being axially reciprocable within the cylinder, and a rough mixture of the components of the component system being formed from the primary flow and the secondary flow(s) flowing in a first flow direction when the piston is returned into a lower stroke position which rough mixture can be conveyed into or through the mixer device when the piston is then advanced into an upper stroke position.
In such a device the flow direction of the conveyer means and/or the flow direction of the rough mixer means is reversible.
According to another embodiment the inlets for the secondary flows open at the outlet side end of the cylinder and/or at a position axially spaced therefrom, the mixer means being a mixer means having a radial and an axial mixing effect.
In the devices according to the invention described above the inlets of the rough mixer means having the cylindrical basic shape advantageously open in a substantially radial direction. According to the first embodiment of the device of the invention a rough mixture is prepared which has a substantially uniform composition within the “disk-shaped” volume elements VEi extending across the radial cross section of the cylindrical rough mixer means which is virtually independent of their axial height. Said rough mixed structure which was illustrated above by comparison with the coloured stripes on a strand of tooth paste and which is formed when the piston is returned while the stroke volume in the cylinder is filled, is best prepared by introducing the components of the component system to be processed into one and the same volume element VE of the cylinder at the outlet side end of the cylinder, i.e. at the same or substantially the same axial level, via the various supply means.
The device according to the second embodiment is provided with a mixer means having an axial and a radial mixing effect. In this case the mixer means produces a homogenous or semi-homogenous mixture from which then mouldings are produced irrespective of the type and structure of the rough mixture prepared in the cylinder of the injection unit. According to this second embodiment of the device the inlets of the supply means may correspondingly be disposed in the rough mixer axially level and/or on different axial levels.
Preferably the supply means substantially consists of a unit comprising a plasticizer screw and a piston.
According to an advantageous embodiment the rough mixer is formed
Preferably the moulding tool is an injection moulding tool. It may, however, also be a continuous casting tool, and the strand produced may be cut to form shaped bodies by a punching or cutting means.
In the devices according to the invention the means by which the primary flow is generated and introduced into the device as well as the introducing means for secondary flows are either suitable for metering in the respective introduced flows of substances or they are provided with a metering device. Such means and metering devices are known to those skilled in the art. Typical supply means which also have a metering function are extruders; the metering function may be obtained by switching the drive or controlling the rotational speed.
However, any other, per se known metering means may be used within the scope of the invention, e.g. gear pumps, valves, shutters, sliders, piston metering devices and the like.
With the metering devices the throughputs or the absolute amounts of the individual components and thus their quantity ratio can be set so that certain predetermined compositions or formulas can be realised in a particularly simple manner.
The devices according to the invention for the production of mouldings may further include one or more testing means for testing the properties of the prepared mouldings which are arranged downstream of the moulding tool or a retrieval and magazine system or combined with one or more testing means.
The device according to the invention is preferably a modular construction, the supply means, the rough mixer means and the mixer means as well as possibly the moulding tool being formed as modules which are preferably detachably connected to each other by means of quick-action fastenings.
The conveying, storage and testing equipment may also be modular.
According to particularly preferred embodiments the device according to the invention comprises one or more introduction means for secondary flows and/or conveying means for the primary flow which are devices according to the invention for the preparation of corresponding mixtures of components.
The device according to the invention for the preparation of mouldings may advantageously comprise one or more magazines for the storage or intermediate storage of mouldings as well as a conveying system.
The device may further advantageously include a magazine system comprising one or more magazines and their conveying, signalling or data links in which the prepared mouldings can be stored or temporarily stored.
A particularly preferred embodiment of the device according to the invention comprises
One or more of the functions (i) to (vii) may be carried out sequentially and/or in parallel.
The device for handling and possibly testing mouldings may comprise one or more magazines in which mouldings may be stored or temporarily stored.
Controllable and particularly centrally controllable conveyor systems as well as testing systems are per se known to those skilled in the art.
The conveyor system of the handling equipment according to the invention may advantageously be formed as a conveyor belt system, trolley system, moving carpet system, rail track system, circulating system or robot system.
Circulating systems have the advantage of a simple mechanical construction and a simple control.
According to a particularly preferred embodiment of the invention the device of the invention for preparing mouldings and specimen comprising the device for handling and testing the mouldings are integrated so that they form an consolidated device. By combining the production and testing of mouldings including the result evaluation test results can be obtained in an extremely economic and at the same time timesaving way.
These advantages are of particular importance when test series are to be carried out on numerous mouldings having frequently changing compositions.
The coding systems are not subject to limitations within the scope of the invention. Therefore the codes may be holographic codes, barcodes, magnetic codes, transponder codes, chip codes, colour codes or shape codes.
Within the scope of the invention encoding the mouldings as well as the magazine locations and testing equipment by allocating or applying a code is not compulsory.
According to a simple embodiment of the device according to the invention the addresses to which and from which specified mouldings are to be supplied and collected (delivery locations, gathering locations, return positions) may be derived simply from a predetermined order in which specified mouldings are produced or the order of the delivery locations, gathering locations and return positions. In such cases the allocation of specified mouldings to specified addresses results specifically from the process flow itself without any individual encoding being required. In practise such allocations are advantageously generated by a controller and possibly transmitted via data links between the controller and corresponding means such as testing equipment or magazines. Said sequence-depending allocations may be stored allocations.
The devices according to the invention preferably include a control means controlling one or several or all of the functions of the device. It may comprise an input means for inputting data and an output means.
The control means may in principle be designed so that it is signal and data linked to the controlled elements of the device or elements of the device to be controlled or corresponding actuators. Said connection may be established via lines or without lines and may, in the latter case, be a radio link, such as a Bluetooth link. The signal or data links may be designed so that signals or data can be transmitted in both directions to enable, for example, a back indication from a controlled element of the device to the control means indicating that an operation was carried out.
The control means is advantageously designed so that it is capable of controlling the respective consolidated process, at least, however, one of the following items or functions:
The control means is preferably a computer, particularly a micro computer or a computer network including a mainframe computer.
The control means may, however, as well be a programmable logic control or include such a control.
The control means preferably has an encoding function as well. For each moulding produced the conveying path up to the testing means and from there to other testing means or to magazines or from magazines to other delivery or return locations are encoded. This embodiment is particularly advantageous since generally a specified type of moulding is required for each test which can be specifically produced, conveyed and possibly even stored.
The encoding together with corresponding programs enables the localisation and identification of mouldings and the allocation of test results to individual mouldings.
The control means may advantageously include a neural network which can be used to allocate e.g. test results of the composition of the respective moulding and/or process conditions so that after programming result predictions for compositions can be made and therefore the corresponding experiments can be omitted.
Control means and encoding systems are known to those skilled in the art so that no detailed explanation is required.
Within the scope of the invention it is of course possible to manually control individual steps or sequences of the process or even all of the respective process and to manually operate the corresponding parts of the device, e.g. the tool drive or the testing equipment.
Embodiments of the invention will be explained in detail below with reference to the drawings in which
In the following description of the embodiments the same numerals are used for identical elements.
The device comprises two main components, a conveyor and rough mixer means 40 and a mixer means 53 disposed at the outlet 55 of the conveyor and rough mixer means 40.
The conveyor and rough mixer means 40 comprises a conveyor means 41 including one or more inlets 42 for at least one of the viscous or pasty fluids of the component system A or B as a material for the primary flow 43 and a rough mixer means 45 the main inlet 47 of which is connected to the downstream end 46 of the conveyor means 41.
The conveyor means 41 is formed so that it is capable of supplying the material of the primary flow 43 originating from a material supply 88 with a constant and selectable throughput and/or in a determinable quantity in a predetermined flow direction 44.
The primary flow 43 which, in particular, consists of a plastic material and advantageously forms the matrix material for the component system mixtures to be prepared is introduced into the rough mixer means 45 at the main inlet 47. The other components of the component system are brought in contact with or introduced into the primary flow 43 via the inlets 48. To this end introducing means 49 are provided for the secondary flows 50. The inlets 48 are preferably disposed close to the main inlet 47 and advantageously positioned substantially in the same plane 52 transverse to the flow direction 44 of the primary flow 43, i.e. approximately on the same axial level. The introducing means 49 are preferably formed so that the secondary flows 50 can be introduced with a constant and selectable throughput and/or in a selectable overall quantity.
As shown by the two arrows in the rough mixer means 45 symbolising the flow directions of the secondary flows 50 and of the primary flow 43 the rough mixed structure explained above will form during said operation. It was illustrated by coloured stripes on a strand of tooth paste and has, altogether, but not yet axially mixed, the respectively desired composition transverse to the flow direction within volume elements.
The downstream side outlet 55 of the rough mixer 45 is connected to the inlet 54 of the downstream mixer means 53 having a radial mixing effect. Said mixer means is preferably a static mixer. At the outlet 56 of the mixer means 53 the homogenous or quasi-homogenous mixture A or B is discharged and can then be tested and/or processed, particularly moulded.
Therefore preferably a moulding tool will be disposed downstream by which, preferably by means of injection moulding, mouldings, particularly specimen, may be produced.
The device according to the invention generally illustrated in
Such a device is illustrated in
At the start of the preparation of the rough mixture the piston 5 is in an upper stroke position and is, as indicated by the arrow 1 showing the flow direction 44, moved to a lower stroke position, the primary flow 43 and the secondary flows 50 being in a way “sucked” into the cylinder 4. At that time the rough mixture having the explained mixture structure will form. During the following movement of the piston 5 into an upper stroke position the reversed flow direction 44 identified by 2 will result. Said extruding process leads to a discharge of the rough mixture from the outlet 55 of the rough mixer means 43, its introduction into the mixer means 53 through the inlet 54, its homogenisation there and its discharge through the outlet 56. During the extrusion or injection operation the primary flow 43 and the secondary flows 50 are blocked by valves, advantageously by check valves, if necessary.
The procedures of filling the rough mixer 45 and of discharging the corresponding mixtures therefrom will be effected in an alternating manner.
The device according
On the outlet side 9 of the cylinder 4 inlets 10 and 12 are provided which are disposed radially on substantially the same axial level and open into a volume element VE disposed there. Alongside the outlet side volume element VE volume elements VEi are shown which are to represent disk-shaped volume sections of the metered-in component system. Said volume sections extend across the radial cross section of the cylinder 4.
Supply means 14 and 16 for the components of the component system which are themselves provided with inlets 18 or 20 are connected to the inlets 10 and 12 in the cylinder 4.
The mixer means 2 which is a static mixer in the embodiment shown in
During the operation the components of the component system are introduced into the cylinder through the supply means 14, 16 when the piston 5 is returned from an upper stroke position into a lower stroke position. At that time a rough mixture forms in the cylinder 4, said rough mixture having a substantially uniform overall composition within the volume elements VEi shown opposite the outlet side volume element VE on different axial levels of the cylinder 4. The rough mixture was explained above by the analogy with the “stripes on the toothpaste”.
The embodiment shown in
In case of specific supply means, such as kneaders or extruders, the means itself may have a metering function which may, e.g., be controllable via the worm drive.
Furthermore metering means may be integrated with the cylinder 4 of the injection unit 1.
The piston drive 6 is preferably formed so that the returning and advancing of the piston 5 can be controlled. Further it is advantageous to use the delivery pressure of the supply means for pressing the piston 5 back or to at least support its return. The piston drive 6 is preferably formed so that it is capable of advancing the piston 5 in a shot-like manner when the rough mixture is pressed out through the mixer means 2 into the moulding tool 21 so that the static mixing as well as the injection moulding can be carried out efficiently.
A particularly advantageous embodiment of a device according to the invention is shown in
Another advantageous embodiment is shown in
Supply means similar to the ones used for the devices according to
The injection unit 1 comprises a supply means 14 formed as a kneader or extruder including a metering means and a supply means 16 including an inlet 20.
The overall process is controlled by a control means 26 preferably formed as a computer or microprocessor system comprising an input means and an output means 27. The control means 26 may, however, as well be a computer network including a host computer or a programmable logic control.
The supply means 14, 16, the piston drive 6, the mixer means 2, the tool drive 25 controlling the movement of the half mould 23 and thus the closing and opening the moulding tool 21, a magazine system 24 and a testing means 29 are signal and data linked to the control means 26 as shown by the corresponding broken lines.
The various controls illustrated by broken lines are denoted as follows:
In the example shown in
The control means 26 is advantageously also suitable for the evaluation of test results which may be output via the output means 27.
It is to be expressly emphasised that
The mixer means 2 is surrounded by the half mould 22 of the moulding tool 21 in this case. The magazine system 24 comprising at least one magazine is formed and controllable so that it can remove one or more produced mouldings from the moulding tool 21 and supply them on a conveyor path 30 to the testing means 29 or to a plurality of testing means for determining various material characteristics.
The test results can be displayed, printed or transferred for processing by the output means 27.
The cylinder 4 of a piston injection unit as in
In
A mixer means 2 mixing radially and axially and being connected to the outlet 7 of the injection unit 1 at its inlet 8 is provided downstream of the cylinder 4 in the conveying direction. The outlet 3 of the mixer means 2 is again connected to the moulding tool 21 or connectable to it. The supply means 14, 16, the mixer means 2 and/or the moulding tool 21 may be provided with rapid exchange links, e.g. with bayonet couplings.
In
The piston injection device 83 respectively comprises a drive unit 81 as well as an outlet side valve 82, as described above, and is supplied with material from a material supply 80 by the plasticizer unit 79 driven by a drive unit 81 via a material feeder 85 comprising a valve 86.
Finally
The secondary flows, two of which are respectively shown, are supplied to the rough mixer means. In to
The embodiments shown in
In
Two more embodiments of a device according to the invention for the production of mouldings are shown in
The piston 5 accommodated in a housing so that it can be shifted by the piston drive 6 in the driving direction indicated by the double arrow 33 protrudes into the cylinder 4 of the injection unit 1 comprising the outlet 7 connected to the mixer means 2 in its fully retracted state.
The inlets 10, 11 and 12 for the supply means 14, 15 and 16 which can be reciprocated in the driving directions 31 or 32 indicated by double arrows are disposed at the outlet side end 9 of the cylinder 4. The outlet side end of the supply means 14, 15 and 16 is respectively formed as a metering piston 5′ comprising a return flow barrier at its tip which enables a material flow in the conveying direction but not in the opposite direction. The supply means 14, 15 and 16 are shown in a position in which they have been moved towards the cylinder 4.
Two leads 13/1 and 13/2, 13/3 and 13/4 or 13/5 and 13/6 from another supply means 13, e.g. a piston metering unit for liquid and pasty additives, respectively provided with a return flow barrier meet the inlets 10, 11 and 12.
Downstream of the ports comprising the return flow barriers in the conveying direction rough mixer means 2′ are disposed in the respective inlets 10, 11 and 12 of the cylinder 4. The rough mixer means 2′ are static mixers the outlets 3′ of which are opening radially at the outlet side end 9 of the cylinder 4.
Downstream of the cylinder 4 in the conveying direction the mixer means 2 is disposed which is a static mixer 2 the inlet 8 of which is directly connected to the outlet 7 of the injection unit 1. The outlet 3 of the static mixer means 2 is again connected to the moulding tool 21. The device according to FIGS. 6 to 8 thus does not use screw push extruders as supply means but supply means which also implement the principle of piston metering.
In the retracted supply means 14, 15, 16 the respective components are plasticized by an extruder and will reach the corresponding inlet 10, 11, 12 of the cylinder 4 in this state. In the same way liquid or pasty additives are metered into the inlets 10, 11, 12 by the additional supply means 13 depending on the formulas. When the metering process is completed the corresponding supply means 14, 15, 16 moves towards the cylinder and thus presses the plasticized material and the metered-in liquid and pasty additives into the rough mixer means 2′ for homogenisation. At that occasion the back flow barriers at the front end of the metering piston 5′ and the ports for the additives prevent a back flow of the components.
After the rough-mixed components from the supply means 14, 15, 16 have been introduced into the cylinder 4 through the outlet side end 9 of the cylinder the piston 5 will press them into the injection moulding tool 21 through the mixer means 2 for homogenisation.
When static mixers are used as mixer means the period of time during which the metered-in components are homogenised and pressed into the moulding tool 21 can be reduced to times in the range of seconds. In this way at least about 100 to 300 different mouldings having different compositions may be produced and tested for their material characteristics per day. That means this said rapid method enables the production and testing of mouldings from more than 10,000 plastics mixtures per year.
The sequence of a consolidated process comprising the preparation and testing of mouldings and the evaluation of the results will now be explained in detail with reference to
After the determination or preparation of an operating schedule for the process in step (a), e.g. by statistical process scheduling, the control means 26 will control the temperable supply means 14, 16 via corresponding controls 26/14, 26/16 to plasticize the individual components. The number of the required supply means 14, 16 depends on the complexity of the component systems to be prepared.
Next the piston 5 is moved from an upper stroke position into a lower stroke position by the control 26/6 of the piston drive 6 and possibly the control 26/2 of the mixer means in step (b), the components of the component system being virtually drawn into the cylinder 4 or metered into the cylinder 4 by the supply means 14, 16.
The piston 5 may then be returned from its upper stroke position to its lower stroke position by the pressure of the introduced components, or its return movement induced by the control 26/6 of the piston drive 6 may be supported by it.
When the piston 5 is advanced the component system, particularly a plastic material, is mixed with one or more additives in a preferably heatable mixer means 2 and injected into an injection mould (step (c)) or extruded (step (c′)).
After the tool drive 25 acting on one half mould 23 of the moulding tool 21 has opened the moulding tool 21 under the control of the control means 26 implemented through the control link 26/25 the mouldings are removed by a magazine system 24 controlled by the control means 26 via the control link 26/24 and allocated to the moulding tool (step (d)), provided with an individual registered code and stored or temporarily stored in a magazine (step (e)). According to step (d′) the specimen may also be obtained from an extrudate by cutting or punching. With the aid of said code the results obtained in one or more tests carried out by testing means 29 can be allocated to the respective moulding and thus its respective composition. The code may also be used to localise the mouldings. Advantageously the testing means 29 are also controlled by the control means 26 via a control link 26/29.
From the magazine the mouldings are conveyed to the allocated testing means 29, where they are tested, via a conveyor path 30 (step (f)). The data obtained are stored (step (g)).
Said test results which are for example stored in a database can be evaluated, for example, by evaluation software and visualised by the output means 27, e.g. by graphics (step (h)). According to step (i) the results may be correlated with the composition of the specimen with the aid of suitable software, e.g. a neural network 28.
After a sufficient number of test cycles have been carried out a mathematical model can be obtained which respectively enables a correlation between the input variables and the test results, for example with the aid of a neural network (step j)). With this evaluation method as well as by statistical evaluation, for example, trends relating to the properties of the mouldings may be derived from test series with different compositions of the component system, which again enables an optimisation of the further experiment design (steps (k) and (l)).
The results obtained by the rapid screening methods according to the invention offer the user orientation and trend identification relating to the expected property profiles of the newly tested products. For examining the various properties typically the following testing methods are used:
In
The construction of said device is similar that of the devices according to FIGS. 6 to 8.
Two supply means provided for a polymer 1 and a polymer 2 open into the mixing chamber of the injection unit. They each comprise an extruder into which or at the outlet of which, in case of polymer 1, liquid additives (amounts A and B) and, in case of polymer 2, solid additives (amounts A and B) are introduced.
The material is respectively introduced into the mixing chamber of the cylinder of the injection unit in which the actual rough mixture is formed through a static mixer.
When the injection moulding (“shot”) is carried out the component system is injected into the moulding tool through a static mixer. For those skilled in the art it is obvious that the concrete embodiments shown in FIGS. 6 to 9 may be modified in various ways within the scope of the invention, particularly with respect to the type of supply means for the primary flow and the secondary flows and the type of mixers used. Due to this flexibility the methods and devices according to the invention can be adjusted to any component system.
The devices preferably have a modular design so that modifications of the devices can be carried out easily and rapidly.
In both devices the mouldings coming from the moulding tool or a cutting and punching means 36 enter a conveying system 35 either directly or through an intermediate magazine 34.
The conveying system 35 of the device according to
The individual conveyor paths of the conveyor system 35 according to
The system according to
The conveying system 35 of the device according to
The conveying paths connect the individual addresses to each other in this example. This does not necessarily mean that there are direct connections from one address to another, it is also feasible to provide a higher ranking conveying system which can serve the individual addresses using switch-like devices.
In
The testing means 29 actually indicated in
According to an advantageous embodiment of the device according to
The devices according to
One or more magazines 34 may be provided which may be joined to form a magazine system 24 (see
For each test series the number of specimen required for the various tests is prepared and can be stored or intermediately stored in the magazine system 24 or in one or more magazines 34.
The conveyor system 35 may, however, also be formed so that it directly retrieves the mouldings from the moulding tool or a cutting and punching means 36 and conveys them to scheduled addresses.
The transport of mouldings to and from different addresses, e.g. to and from testing means 29, may be effected sequentially and/or in parallel. Mouldings which have already been tested may be stored in an archiving storage 37 as recoverable samples. This is particularly reasonable in case of mouldings subjected to a non-destructive test which possibly is to be repeated. The conveyor system 35 may, finally, also convey mouldings to a garbage container in which, for example, the material is collected for recycling.
The methods and devices described above are particularly made use of in case of problems which require the preparation of a large number of specimen within a short period of time, such as:
A particularly advantageous aspect of the invention is the possible simultaneity of mixing the components and injecting the component system into the moulding tool by which the expenditure of time for a separate compounding as in the conventional methods can be avoided.
Particular advantages of the concept of the invention are as follows:
The system for trend identification provides information on those variables the alteration of which has the strongest or most significant impact on the obtained/obtainable test results within a short period of time as compared to conventional methods mainly due to the correlation between the parameters (e.g. the material composition, the production conditions or the production method) and the corresponding test results.
When analysing the material properties of component systems it is therefore sufficient to prepare specimen from plastics mixtures previously identified as relevant or plastics mixtures which have been identified as relevant with the aid of the trend identification system in the course of a test series. These representative mouldings can than be specifically tested to verify the predicted properties.
The methods and devices according to the invention are not only applicable to and usable for the production of mouldings for material testing but particularly also for production methods. A variety of different products made from all materials which can be processed by the system can be produced, such as polymer blends, cosmetics (e.g. lipsticks) or pharmaceutical products (e.g. suppositories) but also food, particularly pastries (e.g. bread and cake) and toys (e.g. plasticine and the like).
| Number | Date | Country | Kind |
|---|---|---|---|
| 101 41 459.5 | Aug 2001 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP02/09456 | 8/23/2002 | WO |
