WO2002087849A1

WO2002087849A1 - Device and method for the continuous processing of thermoplastic plastic masses and additives

Info

Publication number: WO2002087849A1
Application number: PCT/NL2002/000277
Authority: WO
Inventors: Erik Christian Van Beusekom; Hubertus Lodovikus Van Leeuwen; Petra Christina Johanna Essers; Petri Sintonen
Original assignee: Cps Color B.V.
Priority date: 2001-04-26
Filing date: 2002-04-25
Publication date: 2002-11-07
Also published as: NL1017951C2

Abstract

The present invention relates to a device and a method for the continuous processing of thermoplastic plastic masses, in which the device is provided with an element for feeding the plastic masses to the device and with one or more ports for feeding additives to the device, which additives are present in storage containers.

Description

Title: Device and method for the continuous processing of thermoplastic plastic masses and additives.

The present invention relates to a device for the continuous processing of thermoplastic plastic or synthetic masses, in which the device is provided with an element for feeding the plastic masses to the device and with one or more ports for feeding additives to the device, which additives are present in storage containers. The present invention furthermore relates to a method for the continuous processing of a thermoplastic plastic mass in a device in which the plastic mass is fed to the device via a feeding element and additives from the storage containers are fed to the device via one or more ports.

From US patent No 5,766,522 there is known a method for producing powder coatings, wherein a stream of a solid powder coating precursor is contacted with a process media fluid in a continuous extruder for effectively reducing the viscosity of said stream to allow the continuous processing thereof at a lower temperature. A fluid selected from the group of supercritical fluids and liquefied gases is used as a suitable process media. Said document does not disclose any information at all with regard to the continuous colouring of thermoplastic materi ls to the desired degree.

From the article "Farbe beim Aufbereiten von Kunststoffen automatisiert messen und korrigieren" , Kunststoffe 80. (1990), 7 , there is known a method for colouring plastics by using powdery pigment masses, wherein the obtained coloured material is granulated, the granulate is further processed into test pieces by injection moulding, after which the test pieces are subjected to a quality check. With this method, online colour adjustment is not possible. In addition to that, according to said article the polymers and the pigment concentrates are pre-mixed first, after which the mixture is extruded as a whole, which operation makes it difficult in practice to effect a homogeneous and reproducible colour adjustment, however.

From French patent application No 1,478,165 there is known an extruder for processing thermoplastic plastics, wherein supply lines for supplying additives open into the extruder channel at a location behind the feeding zone, seen in the direction of transport. Only solids, such as stabilisers or plasticisers, are mentioned as additives in said document.

The device referred to in the introduction is known per se from European patent application No 0709 175, wherein additives, such as colourants, are fed to a double-screw extruder in which plastic masses are processed, at such a position that the additives are first mixed at one end of the extruder, after which they are transported by the rotating screw towards the location where the metering of plastic mass takes place, which is halfway the extruder, after which the two components are thoroughly mixed and moved to the other end of the extruder. This manner of supplying additives is claimed to ensure a uniform mixing with the plastic mass that is supplied in the form of a granulate. In practice it has become apparent, however, that such an arrangement does not adequately meet the requirements that are currently made with regard to the complete mixing of additives and plastic mass. The products obtained when such an arrangement is used exhibit areas or stripes where incomplete mixing of plastic mass and additives is evident. Such incomplete mixing has an adverse effect as regards the desired properties, in particular if, for example, fire retarding agents are used as additives. In addition to that, an inhomogeneously coloured final product will be obtained when pigments are used, as a result of which the commercial value thereof is significantly reduced.

Thus it is an object of the present invention to provide a device and a method for the continuous processing of thermoplastic plastic masses and additives, in which the aforesaid problems of the prior art do not occur. Another object of the present invention is to provide a device and a method for the continuous processing of thermoplastic plastic masses and additives, in which the changeover time for processing different additives can be short.

Another object of the present invention is to provide a device and a method for the continuous processing of thermoplastic plastic masses, in which the cleaning operation in connection with the changing of additives that is necessary with the current arrangements is no longer required.

Another object of the present invention is to provide a device and a method for the continuous processing of thermoplastic plastic masses and additives, in which a product having precisely defined parameters, such as the colour, the colour intensity, the viscosity, the rheology and the compatibility with pigment pastes, is obtained in accordance with a preset recipe, which product conforms to the intended recipe and which exhibits a homogeneous character of starting material and additives.

The method as referred to in the introduction is characterized in that one or more liquid concentrate compositions are used as additives, wherein the metering units are in communication with an electronic control unit comprising a memory information system, means for inputting data and means for processing said data, wherein a number of data comprising the desired recipe of plastic mass and additives is input into the electronic control unit, after which processing of said data by the electronic control unit takes place and signals are delivered to the respective metering units for the precise feeding of one or more liquid concentrate compositions to the device via the ports so as to obtain the intended composition of plastic mass and liquid concentrate composition(s) .

Such a method thus makes it possible for the data associated with the desired recipe to be input into the electronic control unit, after which said data is subjected to a processing step and the respective metering units are driven in such a manner that thus the individually feeding of one or more liquid concentrate compositions to the device takes place very precisely. As a result, a composition of plastic mass and one or more liquid concentrate compositions will be obtained in accordance with the intended composition as input into the electronic control unit. It is preferred to use separate concentrate compositions containing colourants as the liquid concentrate composition.

In a special embodiment, it will be preferable for the electronic control unit to be so designed that the user will input inter alia the following basic data, viz. the type of plastic mass, the yield of the desired product and the desired colour of the product, after which it is determined which additives or liquid concentrate compositions will have to be fed to the device with what yield per unit time. To that end, the memory information system comprises inter alia data with regard to the type of plastic mass and the recipe of additives, with colouristic values of the plastic mass being input in connection with the colouring process. The electronic control unit furthermore enables the user to use the electronic control unit as a production management tool.

Preferably, each metering unit of each port is individually driven by the signals from the electronic control unit, so that in the case of complex recipes it is ensured that the intended composition of plastic mass and one or more liquid concentrate compositions is obtained.

In order to keep the changeover time as short as possible and to reduce the amount of waste produce during the changeover to a different liquid concentrate composition, it is preferred to feed the liquid concentrate compositions to the device at a location downstream of the location where the metering of the thermoplastic mass to the device, takes place, wherein in particular one or more liquid concentrate compositions are used as the additives. A liquid concentrate composition is in particular preferred because an efficient mixing with the plastic mass is achieved, so that the percentage of concentrate can be lower than in the case that granulate-like concentrates are used. In addition, the individual components of the liquid concentrate composition can be precisely metered, so that a concentrate having a known, homogeneous composition is obtained. In addition to that, the rheology of the concentrate composition must be adjusted so that metering is readily possible, in which also the during shell life plays a role, preferably the concentrate will remain stable for a period of about 12 months. A preferred liquid concentrate composition comprises: A) 10-97 wt. % of a carrier, comprising Al) a plasticizer, and/or A2) an organic resin material, and/or A3) ether and/or ester compounds of monoalcohols, polyols and/or polyether polyols

B) 0.1-30 wt. % of a surfactant,

C) 3-90 wt. % of a colourant or an additive, wherein all weight percentages are based on the final concentrate composition.

Preferably, a non-aqueous carrier is used as the component A).

Component B) is preferably a surfactant which is capable of forming a dispersion of component C), wherein component B) is selected from the group consisting of non-ionic, cationic, anionic or amphoteric surfactants, or a combination thereof.

Component C) is preferably an inorganic-type colourant selected from the group consisting of titanium dioxide, carbon black, iron oxide, zinc chromate, cadmium sulphides, chromium oxides, cobalt pigment, nickel titanate, bismuth vanadate, sodium aluminium silicate complexes, metal flakes, or a combination thereof, or an organic-type colourant selected from the group consisting of azo and diazo pigments, phtalocyanines, quinacridon pigments, quinophthalone, diketopyrrolo- pyrrole, perylene pigments, isoindolinone, antraqui nones, thioindigo, solvent dyes, or a combination thereof. The selection of the pigments will inter alia be determined by the compatibility with the thermoplastic plastic mass, the need for a coloristic selection such that the lowest possible number of pigments is required for covering the entire spectrum, the degree of "light fastness" and the cost of the use of pigments.

Component C) is furthermore preferably an additive selected from the group consisting of UV stabilisers, anti-oxidants, fire retar- dants, blowing agents, antistatic agents, lubricants, agents for improving the impact strength, mold release agents, fillers or reinforcing materials, or a combination thereof.

Furthermore it is preferred to obtain the aforesaid liquid concentrate composition by adding component B) to component A) at a temperature lower than 80 °C, after which the mixture thus obtained is stirred vigorously in order to obtain a homogeneous composition, after which component C) is gradually added thereto whilst stirring and the whole is subsequently dispersed at a high rate and under high shearing forces until the liquid concentrate composition has been obtained as a stable dispersion.

The present invention furthermore relates to a device as referred to in the introduction, which is characterized in that the additives are liquid concentrate compositions, wherein the metering units are in communication with an electronic control unit comprising a memory information system, means for inputting data and means for processing said data, wherein the electronic control unit, after having processed the data that have been input, delivers one or more signals to the respective metering units for the precise feeding of additives to the device via the ports.

Using the present device, it is thus possible to input data relating to the desired recipe into the electronic control unit, after which the electronic control unit carries out a processing step on the basis of the memory information system that is present in the control unit, so that an amount of additives is fed to the device with great precision so as to obtain the intended composition and mixing of plastic mass and additives. The use of an electronic control unit furthermore makes it possible to feed the exact amount of additives to the device with great precision, so that there will be no question of insufficient amounts being metered, which in practice invariably resulted in a final product not having the exactly desired composition. Furthermore, since the feeding of additives to the device can be precisely adjusted, the amount of residual products upon changing over the device from one recipe to another will be small.

In the present device it is in particular preferred for each metering unit of each port to be individually driven by the signals from the electronic control unit. Such a method of driving makes it possible to feed different additives to the device in different amounts / at different rates, so that complex formulations can be composed while ensuring the desired degree of accuracy.

In a particularly preferred embodiment of the present invention, the ports for the feeding of additives are located downstream of the location where the metering of the thermoplastic plastic mass to the device takes place. Such a location of the ports is in particular desirable in order to keep the change-over time and the amount of waste that is produced upon changing of the additives as small as possible, wherein the exact position of the ports must be selected such, however, that the mixing of additives with the plastic mass will still take place in a homogeneous and reproducible manner.

In order to ensure that the additives are fed to the device in a precise and trouble-free manner, it is preferred to use additives in liquid form and to use a plunger pump or a gear pump as the metering unit.

An extruder or an injection-moulding apparatus can be mentioned as a suitable device.

According to the present invention, the feeding of additives to the device can furthermore take place by means of one or more common ports, wherein the common port comprises a number of individual ports, in which the respective metering units are present. In such an embodiment, pre-mixing of the additives takes place to a certain extent, after which the whole is fed to the device via a common port. Such an embodiment is in particular preferred if one or more additives can be mixed together without restrictions, so that the number of ports for feeding additives to the device will remain limited.

Claims

1. A method for the continuous processing of a thermoplastic plastic mass in a device in which the plastic mass is fed to the device via a feeding element and one or more additives are fed to the device via one or more ports comprising one or more metering units, characterized in that one or more liquid concentrate compositions are used as additives, wherein the metering units are in communication with an electronic control unit comprising a memory information system, means for inputting data and means for processing said data, wherein a number of data comprising the desired recipe of plastic mass and additives is input into the electronic control unit, after which processing of said data by the electronic control unit takes place and signals are delivered to the respective metering units for the precise feeding of one or more liquid concentrate compositions to the device via the ports so as to obtain the intended composition of plastic mass and liquid concentrate comρosition(s) .

2. A method according to claim 1, characterized in that each metering unit of each port is individually driven by the signals from the electronic control unit.

3. A method according to claims 1-2, characterized in that the liquid concentrate compositions are fed to the device at a location downstream of the location where the metering of the thermoplastic mass to the device takes place.

4. A method according to any one or more of the preceding claims, characterized in that a concentrate composition containing individual colourants is used as liquid concentrate composition.

5. A method according to any one or more of the claims 1-4, characterized in that each individual liquid concentrate composition comprises: A) 10-97 wt. % of a carrier, comprising Al) a plasticizer, and/or A2) an organic resin material, and/or A3) ether and/or ester compounds of monoalcohols, polyols and/or polyether polyols,

B) 0.1-30 wt. % of a surfactant,

6. A method according to claim 5, characterized in that a non- aqueous carrier is used as the component A).

7. A method according to claim 5, characterized in that component B) is a surfactant which is capable of forming a dispersion of component C) , wherein component B) is selected from the group consisting of non-ionic, cationic, anionic or amphoteric surfactants.

8. A method according to claim 5, characterized in that component C) is an inorganic-type colourant selected from the group consisting of titanium dioxide, carbon black, iron oxide, zinc chromate, cadmium sulphides, chromium oxides, cobalt pigment, nickel titanate, bismuth vanadate, sodium aluminium silicate complexes, metal flakes, or a combination thereof, or an organic-type colourant selected from the group consisting of azo and diazo pigments, phtalocyanines, quinacridon pigments, quinophthalone, diketopyrrolopyrrole, perylene pigments, isoindolinone, antraqui nones, thioindigo, solvent dyes, or a combination thereof.

9. A method according to claim 5, characterized in that component C) is an additive selected from the group consisting of UV stabilisers, anti-oxidants, fire retardants, blowing agents, antistatic agents, lubricants, agents for improving the impact strength mold release agents, fillers or reinforcing materials, or a combination thereof.

10. A method for preparing a liquid concentrate composition as defined in according to any one or more of the claims 5-9, characterized in that component B) is added to component A) at a temperature lower than 80 °C, after which the obtained mixture is stirred vigorously in order to obtain a homogeneous composition, after which component C) is gradually added thereto whilst stirring and the whole is subsequently dispersed at a high rate and under high shearing forces until the liquid concentrate composition has been obtained as a stable dispersion.

11. A device for the continuous processing of thermoplastic plastic masses, in which the device is provided with an element for feeding the plastic masses to the device and with one or more ports comprising one or more metering units for feeding additives to the device, which additives are present in separate storage containers, characterized in that the additives are liquid concentrate compositions, wherein the metering units are in communication with an electronic control unit comprising a memory information system, means for inputting data and means for processing said data, wherein the electronic control unit, after having processed the data that have been input, delivers one or more signals to the respective metering units for the precise feeding of one or more additives to the device via the ports.

12. A device according to claim 11, characterized in that each metering unit of each port is individually driven by the signals from the electronic control unit.

13. A device according to claims 11-12, characterized in that the ports for the feeding of additives are located downstream of the location where the metering of the thermoplastic plastic mass to the device takes place.

14. A device according to claims 11-13, characterized in that the feeding of additives to the device takes place in liquid form by means of a plunger pump or a gear pump as the metering unit.

15. A device according to claims 11-14, characterized in that the device is an extruder or an injection-moulding apparatus.

16. A device according to claims 11-15, characterized in that the feeding of additives to the device takes place by means of one or more common ports, wherein the common port comprises a number of individual ports, in which the metering units are present.