WO2020165307A1 - Système de régulation de température pour technologie de rotomoulage - Google Patents

Système de régulation de température pour technologie de rotomoulage Download PDF

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Publication number
WO2020165307A1
WO2020165307A1 PCT/EP2020/053689 EP2020053689W WO2020165307A1 WO 2020165307 A1 WO2020165307 A1 WO 2020165307A1 EP 2020053689 W EP2020053689 W EP 2020053689W WO 2020165307 A1 WO2020165307 A1 WO 2020165307A1
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WO
WIPO (PCT)
Prior art keywords
temperature
mould
heating
cooling
wall
Prior art date
Application number
PCT/EP2020/053689
Other languages
English (en)
Inventor
Eric Maziers
Original Assignee
Total S.A.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Total S.A. filed Critical Total S.A.
Publication of WO2020165307A1 publication Critical patent/WO2020165307A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C41/00—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor
    • B29C41/02—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor for making articles of definite length, i.e. discrete articles
    • B29C41/04—Rotational or centrifugal casting, i.e. coating the inside of a mould by rotating the mould
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C33/00—Moulds or cores; Details thereof or accessories therefor
    • B29C33/02—Moulds or cores; Details thereof or accessories therefor with incorporated heating or cooling means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C33/00—Moulds or cores; Details thereof or accessories therefor
    • B29C33/02—Moulds or cores; Details thereof or accessories therefor with incorporated heating or cooling means
    • B29C33/04—Moulds or cores; Details thereof or accessories therefor with incorporated heating or cooling means using liquids, gas or steam
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
    • B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
    • B29C35/0288—Controlling heating or curing of polymers during moulding, e.g. by measuring temperatures or properties of the polymer and regulating the process
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C41/00—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor
    • B29C41/34—Component parts, details or accessories; Auxiliary operations
    • B29C41/46—Heating or cooling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C41/00—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor
    • B29C41/34—Component parts, details or accessories; Auxiliary operations
    • B29C41/52—Measuring, controlling or regulating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
    • B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
    • B29C2035/0211—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould resistance heating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
    • B29C35/16—Cooling
    • B29C2035/1616—Cooling using liquids
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
    • B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
    • B29C35/0288—Controlling heating or curing of polymers during moulding, e.g. by measuring temperatures or properties of the polymer and regulating the process
    • B29C35/0294—Controlling heating or curing of polymers during moulding, e.g. by measuring temperatures or properties of the polymer and regulating the process using tempering units for temperature control of moulds or cores
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C41/00—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor
    • B29C41/02—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor for making articles of definite length, i.e. discrete articles
    • B29C41/04—Rotational or centrifugal casting, i.e. coating the inside of a mould by rotating the mould
    • B29C41/06—Rotational or centrifugal casting, i.e. coating the inside of a mould by rotating the mould about two or more axes

Definitions

  • the present invention is in the field of rotational moulding for the production of objects manufactured of a material containing a curable raw material.
  • the present invention concerns systems and methods for improved temperature control during the moulding process and objects produced using said system and methods.
  • Rotational moulding (commonly shortened to rotomoulding) is a manufacturing method for producing large hollow plastic products. It provides several advantages over other processing technologies such as injection moulding or blowing moulding in the production of plastic articles. Rotomoulding offers the possibility to produce complex shapes with uniform wall thickness, consisting of one or more layers of different materials.
  • Conventional rotomoulding involves a heated hollow mould which is filled with a known amount (charge) of curable material such as plastic powder. Once charged, the mould is closed and slowly rotated (usually around two perpendicular axes) in a heated environment such as a furnace or oven. The heat will cause the softened material to disperse and stick to the walls of the mould. When all the material has melted, the mould and contents are withdrawn from the heat source and placed in a cooled environment to allow the material to cool and solidify. In order to maintain even thickness and avoid sagging or deformation, the mould continues to rotate at all times during the heating and cooling phases. Once the mould and contents have completely cooled, the rotation is stopped and demoulding takes place. The moulded object may then be removed from the mould, or alternatively the mould may be charged with a new material for the production of an additional layer.
  • the devices and methods according to the present disclosure may solve the aforementioned problems. Accordingly, provided herein are systems and methods for improved temperature control during the moulding process, and objects produced using said system and methods.
  • An aspect of the invention provides a device for rotational moulding, the device comprising:
  • a mould which is movably arranged, having a mould system surrounding a mould cavity;
  • a feeding system for feeding a curable raw material into the mould cavity
  • a rotating system for rotating the mould about one or more rotational axes
  • control unit operatively associated with the temperature control system, feeding means and/or rotational means
  • the temperature control system comprises an electric heating system and a pressurized liquid cooling system, preferably configured to heat and cool simultaneously.
  • the pressurized liquid cooling system comprises liquid coolant contained in an enclosure at a pressure of at least 10 to at most 25 bar, preferably 12 to 22, more preferably 15 to 20, more preferably 16 to at most 18 bar.
  • the electric heating system comprises an electric circuit operating at an input/output current of at least 1 to at most 50 mA, preferably 2 to 40, more preferably 3 to 30 mA, most preferably 4 to 20 mA; for example 5 mA; for example 10 mA; for example 15 mA.
  • the heating system and the cooling system are arranged to form a network of alternating heating and cooling points.
  • the temperature control unit is configured for controlling the heating and cooling systems to form at least two temperature zones, wherein the temperature of a first zone is different from the temperature of a second zone.
  • the mould system comprises at least an inner wall and at least an outer wall; preferably wherein the inner wall has higher thermal conductivity than the outer wall.
  • the inner wall and the outer wall are arranged to form a mould cavity enclosed by said walls; wherein the temperature control system is integrated in the mould cavity.
  • the heating system is arranged proximate to the inner wall and/or the cooling system is arranged proximate to the inner wall.
  • the temperature control unit comprises a temperature monitoring unit configured for measuring the temperature of the air in the mould or the melt temperature of the material; preferably a thermocouple through the side of the mould.
  • the temperature control unit is configured for responding to changes in measured temperature.
  • a further aspect of the invention provides a method for the production of an object using the device as described above, the method comprising the steps of:
  • the mould is rotated about at least one, preferably at least two axes during steps (b) and/or (c) and/or (d).
  • the heating and/or cooling is performed by following a predefined temperature-time program; wherein the temperature-time program includes the steps of heating and/or cooling to a predefined temperature and maintaining said temperature for a predefined period; preferably wherein the step of heating and/or cooling is performed at a predefined rate heating and/or cooling rate.
  • the cooling and/or heating is performed on at least a part of the curable raw material to a first temperature in a first temperature zone; and simultaneously cooling and/or heating at least a part of the curable raw material to a second temperature in a second temperature zone and/or leaving zones that are free of material; wherein the first temperature is different from the second temperature and the first temperature zone does not overlap with the second temperature zone.
  • a further aspect of the invention provides for an object produced using the method according to any one of the embodiments as described herein.
  • FIG. 1A shows a first exemplary device for rotational moulding (100) according to the present invention.
  • FIG. 1 B shows a second exemplary device (100).
  • FIG. 1 C shows a third exemplary device (100).
  • FIG. 1 D shows a fourth exemplary device (100).
  • FIG. 2 shows an exemplary device (100) from cross-sectional perspective.
  • FIG. 3 shows an exemplary device (100) having different temperature zones.
  • FIG. 4 shows a heating profile of a conventional rotational moulding device placed in an oven.
  • FIG. 5 shows an exemplary heating profile of a rotational moulding device according to the present invention.
  • FIG. 6 illustrates an exemplary Master/Slave loop for controlling the internal air temperature according to the present invention.
  • a measurable value such as a parameter, an amount, a time period, and the like
  • a measurable value such as a parameter, an amount, a time period, and the like
  • the present invention provides devices and methods for improving the management and control of temperature in rotational moulding technology.
  • the concept of rotational moulding also called rotomoulding or rotocast, is known in the art.
  • the basic principles of rotomoulding may be found discussed above.
  • the devices and systems may be suitable for production of full objects, hollow objects, or a layer on full or hollow objects, in a variety of materials and/or interspaced functionalities.
  • the objects can be composed of one layer of the same material, or of two or more layers of the same material or different materials and/or composites.
  • the suitable material as used herein refers to a curable raw material, such as plastic, for example a thermoplastic material, metal, nutrients, or any other raw material that can be processed by means of rotational moulding.
  • the devices and methods may also be suitable for additive manufacturing (AM) which allows for production of 3D objects by stacking layer-upon-layer of material, using suitable raw materials that are used in 3D printing. Therefore, the present invention allows for rotomoulding new materials, for example different materials than polyethylene.
  • AM additive manufacturing
  • the raw material may comprise a polymer selected from the group comprising: polycarbonate, polyether ether ketone (PEEK), polyetherimide (PEI), poly(methyl methacrylate) (PMMA), polylactic acid (PLA), and/or modified polypropylene (PP).
  • PEEK polyether ether ketone
  • PEI polyetherimide
  • PMMA poly(methyl methacrylate)
  • PMMA polylactic acid
  • PP polypropylene
  • the raw material comprises amorphous polymeric material, such as polycarbonate.
  • amorphous polymeric materials also referred to as “non-crystalline polymeric materials” or“amorphous polymeric materials” can refer to polymer materials that do not solidify with a long- range order typically characteristic of a crystalline polymer.
  • Amorphous polymeric materials often have a glass transition temperature or glass transition range rather than a well-defined melting point, as is typical with crystalline polymers. Therefore, amorphous polymers tend to soften or melt over a wide temperature range rather than liquefy at a set melting point.
  • examples of amorphous polymeric materials include, but are not limited to, polycarbonate and other thermoplastic polymers, such poly(p- phenylene oxide), and polyimides, such as polyetherimide.
  • the present invention has various advantages over conventional rotational moulding technology.
  • the device may show improved energy efficiency and reduced processing cost and (heating/cooling) cycle times.
  • the temperature adjustment between the set (desired) temperature and the actual (in-mould) temperature may be achieved faster and more accurately, with greater control over the heating and cooling slopes (i.e. speed of heating and cooling) and thermal plateaus (i.e. constant temperature).
  • the device may also allow for performing advanced production cycles which were not possible before. This may enable production of objects with new features, such as local variations in wall thickness, different material properties, different (decorative or functional) appearance or effect, etc. Additionally, materials which were difficult or impossible to transform before might now be utilised using the device.
  • An aspect of the invention provides a device for rotational moulding, the device comprising:
  • a mould which is movably arranged, having a mould system surrounding a mould cavity;
  • a feeding system for feeding a curable raw material into the mould cavity
  • a rotating system for rotating the mould about one or more rotational axes
  • control unit operatively associated with the temperature control system, feeding means and/or rotational means
  • the temperature control system comprises an electric heating system and a pressurized liquid cooling system, preferably configured to heat and cool simultaneously.
  • the control unit is provided to establish a connection between the components of the rotational moulding device. In particular, it ensures that at least the programs ran by the temperature control system, the optional feeding system, and rotating system are followed through without interference.
  • the control unit may have additional functions which are detailed further below.
  • the mould comprises a mould system forming an enclosure around a hollow space; the enclosed hollow space is referred to as the mould cavity.
  • the mould system preferably comprises an outer layer, a temperature control layer, and an inner layer.
  • the surface of the mould system in contact with the mould cavity (surrounding the cavity) is referred to as the interior mould (wall) surface, whereas the surface in contact with the exterior space (surrounding the mould) is referred to as the exterior mould (wall) surface.
  • the mould cavity is arranged for receiving a curable raw material for the production of an object through the process of rotational moulding.
  • the mould system may be formed of a singular and solid piece, or it may comprise a plurality of (sandwiched) layers.
  • the layers may be arranged as discrete (removable) segments or alternatively form an interconnected structure. There is no limitation to the number of layers, although for the sake of simplicity the present description will be limited to discussion of two layers; for instance a first and a second layer. Each layer may have different material properties, such as thermal conductivity.
  • the raw material and the thickness of the mould system are preferably chosen in such a way that the mould is suitable for use for rotational moulding, such that it allows for the optimal heat exchange between the mould system and the curable material, present in the mould.
  • the wall thickness of the mould is chosen in such a way that the mould is sufficiently strong to process the intended raw material and resist the forces commonly associated with rotational moulding, such as gravity, thermal stress or differential pressure during the moulding process.
  • suitable materials may include: steel, aluminium, composite carbon/ epoxy, composite Fibre Glass/Epoxy, PU, PEI, PEEK, and so on.
  • the mould may comprise 2 half parts, or more, even more than 15 separate parts for more complex designs.
  • the mould system may comprise passageways or conduits. These conduits may be required for proper functioning of the feeding and/or temperature control systems; for instance by connecting the mould cavity with the exterior space.
  • the conduits may also serve as suction means (e.g. suction orifice) for producing a suction effect, preferably in connection with a nozzle and/or pump.
  • the conduits may be formed of the same material as the mould system (i.e. being part of the mould), or may be of a different material disposed within the mould system (i.e. integrated into the mould).
  • the inner surface of the conduits may be coated with a coating providing desirable properties, such as improved corrosion resistance or reduced friction.
  • the mould system may comprise a heat blocking means for reducing the heat transfer between the mould (e.g. mould cavity and temperature control system) and the exterior space.
  • the heat transfer means is a layer of thermally insulating material.
  • the insulating material may be in direct connection with at least a part of the temperature control system.
  • the insulating material is provided proximate to the exterior space.
  • the insulating material surrounds at least a part of or the entire mould. Suitable insulating materials include glass, ceramics, composites, Teflon, Polytetrafluoroethylene (PTFE), and/or Polyvinylidene fluoride (PVDF).
  • the mould system comprises at least an inner wall and at least an outer wall; wherein the inner wall forms a surface in contact with the mould cavity and the outer wall forms a surface in contact with the exterior space.
  • the inner wall will be of a material having a higher thermal conductivity than the outer wall.
  • the inner wall and/or outer wall may be removable or dismountable. This allows easier maintenance of systems or conduits arranged within the mould system.
  • the inner wall may be made of a material from the following list: steel, aluminium, composite carbon/ epoxy, composite Fibre Glass/Epoxy, PU, PEI, PEEK, or a conductive material.
  • the outer wall may be made of a material from the following list: steel, aluminium, composite carbon/ epoxy, composite Fibre Glass/Epoxy, PU, PEI, PEEK, or an insulating material.
  • the at least one inner and at least one outer walls may be arranged to form a hollow space or mould system cavity enclosed by said walls.
  • the presence of such a mould system cavity allows for easier integration of systems or conduits within the mould system.
  • the mould system cavity may provide an additional degree of insulation between the mould cavity and the exterior space.
  • the temperature control system is integrated in the hollow space of the mould system cavity; enclosed by the inner and one outer wall.
  • Sufficient space may be provided within the mould system during production, or alternatively, the mould system may be modified post production. For example, cavities, conduits and recess may be machined out from the mould system.
  • Additional support structure may be provided to prevent (mechanical) distortion under the force of gravity, thermal stress or differential pressure during the moulding process.
  • the support structures are arranged to connect the inner with the outer wall.
  • the optional feeding system comprises one or more devices configured for feeding a curable raw material to the mould cavity for forming an object, also referred to as charging the mould cavity.
  • the amount of material may be controlled volumetrically or gravimetrically.
  • the device may comprise multiple feeding devices, such as a first raw material feeding device and a second raw material feeding device.
  • the feeding devices may feed the materials simultaneously (in a single moulding session) or successively (in a following moulding session), such as for the production of an additional layer.
  • the feeding means may comprise an external device which stays separate from the mould during the moulding process; the device may feed the material to the mould through specific feeding entry points.
  • the feeding means may comprise an external feeding device (e.g. connective tubing in fluid connection with a raw material feeding pump) which can connect with a feeding entry point on the mould (e.g. connective tubing in fluid connection with the mould cavity).
  • the mould may have a temperature that could damage the feeding device (e.g. melting of connective components). In that case, preferably, sufficient thermal isolation is provided between the feeding device and the mould.
  • the rotational system comprises one or more devices configured for rotating the mould about one or more rotational axes.
  • An improved uniformity of the wall thickness of the object can be obtained by rotationally positioning the mould about at least two axes at any other angle relative to each other.
  • the temperature control system is configured for controlling the temperature of the mould cavity, and in turn that of the materials present in the cavity, in addition to temperature related parameters, such as heating/cooling rate.
  • the temperature control system within the mould system enables a faster and more optimal heat transfer to or from the cavity.
  • the heating/cooling cycle times, necessary for producing the object can be shortened and loss of energy can be reduced (increasing the energy efficiency).
  • the heating/cooling volume can be limited to the mould cavity which requires considerable less energy when compared to traditional devices, such as those placed in an external heating area (e.g. oven, microwave) or a cooling area (e.g. convective air or refrigerated area).
  • the integration also improves the mobility and manipulability of the mould, since manipulation of the mould can take place together with the temperature control system; the system does not need to be removed to provide access to the mould. Displacement of the mould is not hindered by a surrounding casing of, for example, a heating or cooling system in which the mould is located, but the temperature control device and mould may be displaced, moved, and manipulated as a whole, and may be subjected to rotation, shaking or tilting movement. Operations such as a transfer of the mould to the heating/cooling area, the opening and closing of the area, manipulation of the mould to a specific position, and so on, become obsolete. This may not only save considerable time and resources, but could also improve the energy efficiency of the process. Moreover, the integrated temperature control system takes up much less space than external heating systems and can therefore be installed faster than conventional rotomoulding devices.
  • the temperature control system may be configured for performing a predetermined temperature-time program (air temperature cycle or material melt temperature).
  • a predetermined temperature-time program air temperature cycle or material melt temperature
  • the temperature-time program will include information related to at least one predefined temperature over one predefined time length (cycle).
  • the temperature-time program may include a series of temperature cycles, which may be run in sequence (e.g. multiple mouldings) or in parallel (e.g. temperature zones discussed further below).
  • the local air temperature or melt temperature may be measured instead of the global air temperature, for example using thermocouples or PT100. This allows for non-uniform objects to be formed.
  • the temperature-time program may further include information related to heating or cooling ramp rates (i.e. speed of heating and cooling).
  • the temperature-time program may be fit to set-points.
  • control of ramp rates also enables greater control over heating plateaus, by maintaining a stable temperature of the mould and adjusting when necessary.
  • the temperature control system ensures (steered by the control unit) that the desired temperature-time program is followed through by the mould which may improve the reproducibility of the production process.
  • the improved temperature controlling capabilities may result in objects with a reproducible quality, reproducible mechanical properties and a reduced number of rejected pieces.
  • the control unit may be configured for storing a predefined temperature-time program which includes information related to at least one predefined temperature and at least one predefined time length. Preferably the temperature-time includes information related to heating and/or cooling ramp rates.
  • the control unit may have various programs or sequences of programs stored. Each program may be specific for a curable material type and/or cured object type.
  • the temperature-time program may be combined with programs related to other operations of rotational moulding technology, including the mould manipulation (e.g. rotation) and displacement course, feeding of curable material, and so on. The control unit may then ensure that the desired temperature-time program is followed through by the mould in combination with the other operations of the mould device.
  • the electric heating system (also referred to as heating system) is configured for increasing heat (i.e. thermal energy) in the mould system which can be transferred into the mould cavity.
  • the heating system may provide heating to the mould cavity by being in direct contact with the interior of the mould.
  • the heating system may heat a layer of the mould system which can in turn transfer heat to the mould cavity; the layer will preferably be of a heat conductive material.
  • Various techniques are known in the art for generating thermal energy for rotational moulding; for instance, radiant heating, convection heating, circulation of a heated liquid or gas, infra-red heating, microwave heating, and so on. It is understood that the skilled person is capable of adapting the mould system to integrate the necessary functions for the desired heating system.
  • the heating method is preferably chosen in such a way that the desired raw material may be processed in the mould.
  • a higher temperature for example 100-200°C or higher, or for example 250° to 320°C, or for example 350° to 400°C may be desired.
  • Metals may demand even higher processing temperatures.
  • the heating system may be mounted onto the mould system, for example using fasteners or other fixation means.
  • the heating system may be enclosed by the mould system, for example by providing conduits for the passage of a heated liquid or gas in the wall.
  • Preferably the heating system is integrated into a mould system cavity enclosed by at least one inner and at least one outer wall. This integration may allow easier access to the heating system for performing maintenance or replacement of the system.
  • the electric heating system comprises an electric circuit generating heat by conduction of electrical current through resistive elements, such as resistance wires.
  • the electric current is supplied by a current source.
  • Electrical heating is considered to be a very efficient and easily controllable heating method.
  • the electric circuit operates at an input/output current of at least 1 to at most 50mA, preferably 2 to 40, more preferably 3 to 30mA, most preferably 4 to 20 mA; for example 5 mA; for example 10 mA; for example 15 mA.
  • the electric circuit may comprise other (safety) features commonly associated with such systems; for example, fuses, circuit breakers, and so on.
  • the electric circuit may comprise a plurality of resistance wires, preferably disposed at spaced intervals throughout and/or along the mould system forming a network of heating points or zones.
  • the term“heating point” or“heating zone” as used herein refers to an area of the mould surface that is heated by the heating system.
  • the term“cooling point” or“cooling zone” as used herein refers to an area of the mould that is heated by the heating system.
  • the term“point” can therefore also be a zone or path along the mould surface.
  • the electrical wires may be interconnected, such as forming a grid or mesh, or may follow discrete paths along the mould system.
  • the wires may be copper, nickel, chrome, or other suitable materials or a combination thereof (such as nichrome).
  • the wires may be covered with an insulating material for protective purposes.
  • the pressurized liquid cooling system (also referred to as cooling system) is configured for reducing heat (i.e. thermal energy) in the mould system which is absorbed from the mould cavity.
  • the pressurized liquid cooling system may comprise a liquid coolant contained in an enclosure at a predefined liquid pressure.
  • the enclosure comprises a series of conduits integrated into the mould system, such as tubing or piping.
  • heat will be transferred from the mould system into the coolant stream.
  • the heated coolant may dispose the unwanted heat through contact with a dedicated heat exchanger, such as a radiator. This provides a constant temperature in the cooling circuit as well as constant flow.
  • the cooled coolant may then return to the heating position to provide further cooling.
  • the cooling system may cool the mould cavity by being in direct contact with the interior of the mould.
  • the cooling system may cool a layer of the mould system which can in turn absorb heat from the mould cavity; the layer will preferably be of a heat conductive material.
  • the risk of boiling the coolant is avoided by increasing the pressure in the cooling system, which raises the boiling point of the coolant. Additionally, the increased pressure allows for improved heat transfer rates (faster and greater heat transfer).
  • the pressure may be applied using a pump, which may be integrated into the mould or be a separate device.
  • the liquid pressure may range from at least 10 to at most 25 bar, preferably 12 to 22, more preferably 15 to 20, 16 to at most 18 bar; for example 17 bar.
  • the cooling system may be an open system wherein excessive pressure is limited by a pressure valve in it. Excessive pressure opens the valve which allows coolant to flows out through an overflow pipe. New or recycled coolant may be provided to the system when necessary, for instance to compensate loss of coolant (topping up).
  • the cooling system is a closed system, preferably wherein any overflow is stored in a connected tank, from which it can be sucked back into the system while the remaining liquid cools. The closed system may improve the efficiency and cost of the cooling system.
  • pressurised coolant allows for the cooling system and the heating system to work at the same time.
  • Use of a closed system avoids the need to switch the system on and off.
  • pressurized coolant allows the system to work with a full liquid piping system.
  • a master slave control loop is therefore preferably used acting on both circuit heating and cooling at the same time to maintain high precision on the temperature control of the mould.
  • the liquid coolant may comprise any chilled, readily flowable fluid that does not distort or interact with the interior walls of the conduit means.
  • the liquid coolant is water or nitrogen; cooled water is a particularly preferred fluid for economic reasons.
  • the coolant may be supplement with property modifying additives, such as antifreeze to lower the freezing point of a water-based coolant.
  • the cooling system is formed by channels that are formed by an undulating layer, preferably a composite layer, between the two layers forming the inner and outer walls.
  • This particular arrangement illustrates a particularly efficient embodiment to form a network of alternating heating and cooling points (or alternating heating zones and cooling zones) by changing the contact surface between on one hand the mould cavity and on the other the components of the cooling and heating systems.
  • the outer wall may comprise an optional additional insulation layer.
  • the heating and cooling systems may be arranged to form a network of alternating heating and cooling points (or alternating heating zones or cooling zones). Each point is defined as a surface area at which heat transfer may take place between the heating and/or cooling system and the mould cavity. By alternating the heating and cooling points, a greater degree of control can be achieved over the heating/cooling rate and local temperature fluctuations.
  • at least part of the heating system is arranged proximate to the interior mould system.
  • at least part of the cooling system is arranged proximate to the interior mould system.
  • the systems provide the possibility to locally (by zone) control the wall thickness of the moulded polymer. It is possible to cool zones and heat zones at the same time at different rates.
  • the temperature control system may be configured for, preferably simultaneously, controlling the heating and cooling systems to form (at least 2) temperature zones, wherein the temperature of (at least) a first zone is different from the temperature of (at least) a second zone.
  • Each zone is characterised by a certain temperature and interior mould surface area (or the corresponding mould cavity air volume). The differences in temperature may be achieved by controlling the heating and/or cooling rate.
  • a first zone of the temperature control system may be set to be heated by local activation of the heating system while a second zone is cooled by local activation of the cooling system.
  • the different zones may also be configured to heat or cool at different intensities.
  • a first zone of the temperature control system may be set cool at a high intensity, whereas a second zone may cool a low intensity.
  • a master/Slave loop may permanently control cooling and heating anywhere in the mould.
  • the zones may be of any size, volume or surface area.
  • the mould may be split into two equal sized zones to obtain different material properties in each zone, or it may be one smaller sized zone surrounding by a much larger zone.
  • the zones may be contiguous, nearby or distant.
  • Differences in temperature could allow for greater control over curing process, which may allow for variations in material properties and thickness of the cured object.
  • Controlled thickness manipulation may allow for creation of products with different (technical or decorative) appearance or effect, especially when different material layers are stacked on top of each other, next to each other, or near each other.
  • the cured object’s supportive walls could be made thicker to obtain increased strength while adjacent walls could be made thinner to reduce the object’s weight and production costs.
  • the cooling rate will typically affect the material thickness.
  • Controlling the mechanical properties is particularly useful in combination with curable materials which have temperature sensitive properties; such as viscosity, creep, stress and strain, and so on.
  • the implementation of heating zones therefore also allows for advanced manipulation of the mould, for example by allowing filling of the cavity with (additional or new) curable raw material on one side while another side is still cooling.
  • the temperature control system may be configured for performing a predetermined temperature-time program for each zone.
  • each zone may, independently of optionally other zones, run an individual (temperature-time) cycle without disturbing or adversely affecting the cycle of the other zones.
  • each zone can be heated or cooled independently of optionally of other zone up to a pre-selected temperature, during a preselected time and according to a pre-selected temperature-time course. Sequences of heating and cooling may be chosen for each zone independently of the other, taking into account the nature of the raw material or raw materials to be processed and the intended appearance.
  • the control unit may be configured for storing a predefined temperature-time program for at least one zone.
  • the control unit may have various programs or sequences of programs stored for a number of zones. Each program may be specific for a curable material type and/or cured object type.
  • the temperature monitoring unit is preferably in communication with the temperature control system and/or the control unit, which may be configured for responding to changes in measured temperature.
  • the temperature monitoring unit may be a temperature sensor of any type suitable for detecting the temperatures.
  • the temperature monitoring unit comprises a plurality of sensors.
  • the plurality of sensors may be sensors of the same type, or be a combination of various sensor types.
  • the sensors are selected from the group consisting of a thermocouple, e.g. a PT100 or IR sensors. In case the temperature of the mould system is varied locally, at least one separate sensor may be provided per temperature zone.
  • a further aspect of the invention provides for a method for the production of an object using a device for rotational moulding according to any one embodiment as described herein, the device comprising, a mould which is movably arranged, having a mould system surrounding a mould cavity; a temperature control system integrally formed within the mould system; optionally a feeding system for feeding a curable raw material into the mould cavity; a rotating system for rotating the mould about one or more rotational axes; a control unit operatively associated with the temperature control system, feeding means and/or rotational means;
  • the mould is rotated about at least one, preferably at least two axes during steps (b) and/or (c) and/or (d).
  • the method is performed using a Master/Slave loop, which allows heating and cooling to occur simultaneously.
  • the moulded object may be removed from the mould, or alternatively the mould may be charged with a new material by repeating steps (a) to (d).
  • the rotating is preferably maintained throughout steps (b) and (d).
  • the heating and/or cooling may be performed by following a predefined temperature time program; wherein the temperature-time program comprises the step of heating and/or cooling to a predefined temperature and maintaining said temperature for a predefined time period (i.e. thermal plateau).
  • the step of heating and/or cooling is performed at a predefined heating and/or cooling rate (i.e. heating and/or cooling speed).
  • the temperature-time program may comprise a sequence of predefined temperature-time cycles; for example heating to a first predefined temperature and maintaining said temperature for a first predefined time, followed by heating to a second predefined temperature and maintaining said temperature for a second predefined time, and so on.
  • the method may comprise the steps of: cooling and/or heating at least a part of the curable raw material to a first temperature in a first temperature zone; and, simultaneously cooling and/or heating at least a part of the curable raw material to a second temperature in a second temperature zone; wherein the first temperature is different from the second temperature and the first temperature zone does not overlap with the second temperature zone.
  • each temperature zone may be controlled using a predefined temperature-time program, preferably a unique predefined temperature-time program for each zone.
  • a further aspect of the invention provides for an object produced using the device for rotational moulding according to one or more embodiments as described herein.
  • a further aspect of the invention provides for an object produced using the method for rotational moulding according to one or more embodiments as described herein.
  • the object may be an automotive part, for example a car hood, a dashboard, a battery pack, a door structure, etc.
  • FIG. 1A-D and FIG. 2 illustrate different embodiments of a device (100) for rotational moulding according to the present invention.
  • the device (100) is illustrated to comprise a mould system (150) surrounding a mould cavity (10).
  • the mould system (150) comprises an outer layer (151), a temperature control layer (152), and an inner layer (153).
  • a temperature control system comprising an electric heating system (200) and a pressurized liquid cooling system (300)
  • the mould system (150) may comprise multiple layers forming a wall which allows mounting or affixing of the components of the heating and cooling systems.
  • the heating and cooling systems are arranged to form a network of alternating heating and cooling points; the heating points are represented by the (+) symbol and the cooling points by the (-) symbol.
  • the heating/cooling points form a surface area enabling direct heat transfer to occur between the heating and/or cooling system and the mould cavity, or alternatively indirect heat transfer by contact with the interior mould system adjacent to the mould cavity.
  • the device (100) is further provided with a plurality of conduits connecting the mould cavity (10) with the exterior space.
  • At least one conduit (170) may serve as feeding point for loading the mould cavity with a curable material.
  • Some conduits (171) may also serve as suction means (e.g. suction orifice).
  • FIG. 1 C illustrates a first exemplary arrangement of the heating system (200) and the liquid cooling system (300).
  • the elements (+) of the heating system (200) are arranged about a central axis running through the centre of the mould system.
  • At least part of the cooling elements (-) is arranged to run proximate to the inner wall (i.e. side of the mould system contiguous to the mould cavity) and at least another part is arranged to run proximate to the outer wall (i.e. side of the mould system contiguous to the exterior space).
  • FIG. 1 D illustrates a second exemplary arrangement of the heating system (200) and the liquid cooling system (300).
  • the elements (-) of the cooling system (300) are arranged about a central axis running through the centre of the mould system.
  • the elements (+) of the heating system (200) are arranged at a certain offset from said central axis.
  • FIG. 2 a detailed cross-section of the mould system (150) is shown, the mould system comprising a composite layer as an inner wall (153) and a composite layer as an outer wall (151).
  • the electric heating system (200) comprises an electric circuit comprising electrical wires arranged to run through the mould system (150); the wires may be interconnect to form a grid or may run discrete unconnected wires.
  • the wires are arranged proximate to the inner wall (153).
  • the cooling system (300) is present by channels that are formed by an undulating composite layer between the two composite layers forming the inner and outer walls (151 , 153).
  • the cooling system (300) comprises a liquid coolant.
  • This particular arrangement illustrates a particularly efficient embodiment to form a network of alternating heating and cooling points by changing the contact surface between on one hand the mould cavity (10) and on the other the components of the cooling and heating systems.
  • the outer wall (151) may comprise an optional additional insulation layer, illustrated by dashed lines.
  • FIG. 3 illustrates how different temperature zones may be formed in the mould cavity (10).
  • the control unit may be configured to divide the heating system and cooling system into areas with varying heating/cooling rates to arrive at different temperatures.
  • the figure shows a first temperature zone which is heated by a first component of the heating system (210) and a first part of the cooling system (310). Further shown are a second zone (211 , 31 1), third zone (212,312), fourth zone (213,313), fifth zone (214,314), sixth zone (215,315), seventh zone (216,316), and so on.
  • the zones may be of any shape, size (volume), position, etc.
  • FIG. 4 and FIG. 5 Reference is made to FIG. 4 and FIG. 5.
  • FIG. 4 shows the heating profile of a conventional rotational moulding device, wherein a mould is placed in a heated area such as an oven.
  • the first graph (1) represents the temperature measured inside the oven; it is shown that the oven takes several minutes to reach the desired temperature of approximately 300-320° C, after which a thermal plateau is maintained at 300°C, and after turning of the heating (14 min) the temperature quickly drops down to 50°C.
  • the second graph (2) then shows the temperature of the mould placed into the heated oven.
  • the mould takes a significantly longer time to absorb the thermal energy from the oven, only reaching the desired moulding temperature of approximately 230-240 °C after about 14 min. Afterwards the air internal temperature (AIT) decreases slowly without any provided cooling.
  • AIT air internal temperature
  • FIG. 5 shows an exemplary heating profile of a mould which is heated with the device of the present invention, using set points and showing the peak internal air temperature (PIAT).
  • the device allows the control unit to run specific heating temperature-time programs, as indicated by ti to fe.
  • the temperature control system may also control the heating or cooling ramp rates, as indicated by the slope ai to as. Indeed, by also controlling the heating/cooling rates, greater control over the curable material is achieved allowing for the production of a cured object with different material properties or appearance or effect. A different curve may be used for different polymeric materials.
  • the curve, or part of the curve comprises a sigmoid function with up to 6 coefficients.
  • the curve can be constructed in advance, thereby modelling the process in advance.
  • the set-points can be modelled and adapted, whereby the temperature profile obtains these set points. Plateaus can also be included.
  • FIG. 6 illustrates an exemplary Master/Slave loop for controlling the internal air temperature according to the present invention. Both heating and cooling can be simultaneously active, which allows for more accurate control and avoids oscillations.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Oral & Maxillofacial Surgery (AREA)
  • Thermal Sciences (AREA)
  • Moulds For Moulding Plastics Or The Like (AREA)

Abstract

La présente invention se rapporte au domaine du rotomoulage pour la production d'objets fabriqués à partir d'un matériau contenant une matière première durcissable. En particulier, la présente invention concerne des systèmes et des procédés permettant une régulation de température améliorée pendant le processus de moulage et des objets produits à l'aide dudit système et desdits procédés.
PCT/EP2020/053689 2019-02-13 2020-02-13 Système de régulation de température pour technologie de rotomoulage WO2020165307A1 (fr)

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EP19305178.6 2019-02-13

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CN114701100A (zh) * 2022-03-30 2022-07-05 贵州省工程复合材料中心有限公司 一种适应智能化制造的深腔型产品注塑模具的制造方法
WO2023031981A1 (fr) * 2021-09-06 2023-03-09 Persico S.P.A. Moule pour rotomoulage
WO2023031982A1 (fr) * 2021-09-06 2023-03-09 Persico S.P.A. Moule pour rotomoulage
IT202100029543A1 (it) * 2021-11-23 2023-05-23 Persico Spa Stampo per lo stampaggio rotazionale
IT202100029549A1 (it) * 2021-11-23 2023-05-23 Persico Spa Stampo per lo stampaggio rotazionale

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2023031981A1 (fr) * 2021-09-06 2023-03-09 Persico S.P.A. Moule pour rotomoulage
WO2023031982A1 (fr) * 2021-09-06 2023-03-09 Persico S.P.A. Moule pour rotomoulage
IT202100029543A1 (it) * 2021-11-23 2023-05-23 Persico Spa Stampo per lo stampaggio rotazionale
IT202100029549A1 (it) * 2021-11-23 2023-05-23 Persico Spa Stampo per lo stampaggio rotazionale
CN114701100A (zh) * 2022-03-30 2022-07-05 贵州省工程复合材料中心有限公司 一种适应智能化制造的深腔型产品注塑模具的制造方法
CN114701100B (zh) * 2022-03-30 2023-06-02 贵州省工程复合材料中心有限公司 一种适应智能化制造的精密深腔型产品注塑模具的制造方法

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