Methods, apparatus and systems for molding articles

Abstract

The invention relates to a molding method (100) and associated molding system (1). The molding method (100) comprises adding (101) an undried polyethylene terephthalate (PET) material into a dryer (40), drying (102) the PET material, introducing (103) the PET material into a material feed stream (41), measuring (104) a moisture content of the material feed stream using a moisture measurement unit (43) and selectively introducing (106) an undried PET material into the material feed stream (41) using a dosing unit (42) based on the measured moisture content.

Description

[0001] METHODS, APPARATUS AND SYSTEMS FOR MOLDING ARTICLES

[0002] FIELD OF THE INVENTION

[0003] This invention relates generally to methods, apparatus and systems for molding articles. More specifically, although not exclusively, this invention relates to apparatus, systems and methods for molding articles formed of a hygroscopic material, such as polyethylene terephthalate (PET).

[0004] BACKGROUND OF THE INVENTION

[0005] Molding is a process by virtue of which a molded article can be formed from molding material, such as a plastics material, by using a molding system, such as an injection molding system or a compression molding system. Various molded articles can be formed by using such molding processes including, for example, vials for medical applications.

[0006] As an illustration, injection molding of vials involves heating a polymeric material to a homogeneous molten state and injecting, under pressure, the so-melted material into a molding cavity defined, at least in part, by a female cavity piece and a male core piece. Typically, the female cavity piece is mounted to a cavity plate and the male core piece is mounted to a core plate of a mold. The cavity plate and the core plate are urged together and are held together by clamp force, the clamp force being sufficient to keep the cavity and the core pieces together against the pressure of the injected material.

[0007] The molding cavity has a shape that substantially corresponds to a final cold-state shape of the molded article to be molded. The so-injected material is then cooled to a temperature sufficient to enable removal of the so-formed molded article from the molding cavity. When cooled, the molded article shrinks inside of the molding cavity and, as such, when the cavity and core plates are urged apart, the molded article tends to remain associated with the core piece. Accordingly, by urging the core plate away from the cavity plate, the molded article can be subsequently demolded by ejecting it off the core piece.

[0008] The mold typically includes cooling channels, which are designed to maintain the cavity and core pieces within a predetermined temperature range throughout the molding cycle. This temperature range is selected to cool of the molten material injected into the cavity. This cooling begins while the material is injected into the cavity. Molding articles that are relatively long and thin therefore requires injection fill rates and pressures that are sufficient to ensure the entire cavity is filled completely. However, high fill rates and pressures can cause excessive shear in the material, thereby degrading the properties of the molded article and in extreme cases premature wear of mold components.

[0009] One approach to mitigate this issue is to introduce an additive, such as a demolding agent, to increase the flowability of the material. This can reduce the injection rates and pressures required to fill the cavity, without causing excessive shear.

[0010] SUMMARY OF THE INVENTION

[0011] The present invention seeks to provide an alternative means of mitigating at least some of the aforementioned issues of the prior art. In particular, additives such as demolding agents can promote residue contamination on mold components, such as vents of the mold stacks and the screw of the melting unit. This can increase the maintenance burden, creating the need for regular (sometimes daily) vent cleaning and frequent removal and cleaning of the screw to remove contamination in melting units.

[0012] Hygroscopic molding resins, such as PET, attract and absorb moisture from humid air. Processing these resins with small amounts of water causes the polymer chains to undergo a chemical reaction known as hydrolysis, which breaks chemical bonds and shortens the polymer chains. This phenomenon is normally considered undesirable, because it degrades mechanical properties of the material and diminishes the performance of the molded article.

[0013] These resins are therefore treated before they are processed, for example by drying the material before it is introduced into the melting unit. However, the inventors have determined that controlled hydrolysis can be used in order to reduce the viscosity of the material, thereby increasing its flowability. This, in turn, enables lower injection pressures to be used without the need for a demolding agent.

[0014] Accordingly, a first broad aspect of this disclosure relates to a method of reducing the viscosity of a material feed stream by combining an untreated hygroscopic polymer material with a treated hygroscopic polymer material and processing the combined hygroscopic polymer material. The combined hygroscopic polymer material may be processed to cause hydrolysis in, and / or reduce the intrinsic viscosity of, the combined mixture. The hydrolysis caused by processing the combined hygroscopic polymer material may reduce the intrinsic viscosity of the combined mixture.

[0015] The inventors have determined that by controllably introducing untreated hygroscopic polymer material into the treated hygroscopic polymer material, hydrolysis in the material feed stream can be reliably controlled to create the desired reduction in material viscosity.

[0016] As such, the method may be used to improve the flowability of the hygroscopic polymer material without the need for additives, such as demolding agents. This may reduce residue contamination on mold components, such as vents of the mold stacks and the screw of the melting unit. The method may therefore reduce the maintenance burden and improve uptime.

[0017] The method may comprise measuring a moisture content of the material feed stream, the combined mixture and / or the treated hygroscopic polymer material. The method may comprise combining the untreated hygroscopic polymer material with the treated hygroscopic polymer material if the measured moisture content is below a predetermined threshold.

[0018] Another broad aspect of this disclosure relates to a method, e.g. a molding method, the method comprising: introducing a treated hygroscopic polymer material into a material feed stream; measuring a moisture content of the material feed stream; and introducing untreated hygroscopic polymer material into the material feed stream if the measured moisture content is below a predetermined threshold.

[0019] By measuring the moisture content, a closed loop process can be used to ensure that a predetermined minimum moisture content is maintained.

[0020] The molding method may comprise processing the material feed stream, e.g. to cause hydrolysis in the hygroscopic polymer material in the material feed stream and / or to reduce the intrinsic viscosity of the hygroscopic polymer material in the material feed stream. Hereinafter reference to the method refers to the method, the molding method or the method of reducing the viscosity of a material feed stream.

[0021] The method may comprise preventing or suspending the introduction of untreated hygroscopic polymer material into the material feed stream. This may be done, for example, if the measured moisture content is above a predetermined threshold, which may be the same predetermined threshold or may be a further predetermined threshold.

[0022] The predetermined threshold may be a predetermined lower threshold. The further predetermined threshold may be a predetermined upper threshold.

[0023] The method may comprise adjusting a quantity, or rate or introduction, of untreated hygroscopic polymer material introduced into the material feed stream, for example based on the measured moisture content.

[0024] The method may comprise adjusting the moisture content of the material feed stream. Adjusting the moisture content of the material feed stream may be done by adjusting a rate at which the untreated hygroscopic polymer material is introduced into the material feed stream. Adjusting the moisture content of the material feed stream may be done based on the measured moisture content.

[0025] The material feed stream may comprise a solid resin. Processing the material feed stream may comprise melting the solid resin. Additionally or alternatively, processing the material feed stream may comprise injecting the resin into an injection mold, for example to produce a molded article.

[0026] The moisture content may be measured downstream of a location at which the untreated hygroscopic polymer material is introduced into the material feed stream. Alternatively, the moisture content may be measured upstream of a location at which the untreated hygroscopic polymer material is introduced into the material feed stream.

[0027] The material feed stream may be operatively connected to an injection unit, e.g. an inlet thereof. The moisture content may be measured upstream of the inlet of the injection unit. The hygroscopic polymer material may comprise polyethylene terephthalate (PET). The treated hygroscopic polymer material may comprises dried PET. The untreated hygroscopic polymer material comprises undried PET, e.g. having a higher moisture content than the treated or dried PET. The untreated hygroscopic polymer material may comprise PET having a higher moisture content than the treated or dried PET. The untreated hygroscopic polymer material may comprise recycled and / or reground material, such as rPET and / or regrind.

[0028] The PET, e.g. the treated and / or untreated PET, may comprise an intrinsic viscosity of less than 0.7 dl / g. The PET within the material feed stream may comprise an intrinsic viscosity of less than 0.7 dl / g. The PET injected by the injection unit may comprise an intrinsic viscosity of less than 0.7 dl / g. The processed PET, e.g. from which the molded article is formed, may comprise an intrinsic viscosity of less than 0.7 dl / g. Preferably, the PET injected by the injection unit comprises an intrinsic viscosity of less than 0.7 dl / g.

[0029] The molded article may comprise a vial, for example a medical vial such as a blood tube. In such cases, the PET may comprises an intrinsic viscosity of approximately 0.56 dl / g. More specifically, at least one of the treated and / or untreated PET, the PET within the material feed stream, the PET injected by the injection unit and the processed PET, e.g. from which the molded article is formed, may comprise an intrinsic viscosity of approximately 0.56 dl / g. Preferably, the PET injected by the injection unit comprises an intrinsic viscosity of approximately 0.56 dl / g.

[0030] The method may comprise changing one or more operating parameters of the injection unit, for example in conjunction with the measured moisture content. The operating parameters may comprise heat power delivered to heaters of the injection unit, screw rotational speed and injection rate. The operating parameters may be changed to generate the desired level of hydrolysis in the material and / or the intrinsic viscosity of the material injected into the mold.

[0031] The molded article may comprise a closure or cap, e.g. a closure cap. The molded article may comprise a container closure or cap, e.g. a container closure cap.

[0032] Another broad aspect of this disclosure relates to a system. The system may comprise a material feed system. The system may be configured or operable to carry out the aforementioned method. The system may comprise a material feed stream or material feed stream passage or conduit. The system may comprise a source of treated hygroscopic polymer material, e.g. for introducing treated hygroscopic polymer material into the material feed stream passage or conduit. The system may comprise a source of untreated hygroscopic polymer material, e.g. for introducing untreated hygroscopic polymer material into the material feed stream passage or conduit.

[0033] The system may comprise a moisture measurement unit, e.g. for measuring the moisture content of material within the material feed stream passage or conduit.

[0034] The system may comprise a controller. The controller may be operatively connected to the moisture measurement unit and / or to the source of untreated hygroscopic polymer material. The controller may be configured to introduce, in use, untreated hygroscopic polymer material into the feed stream passage, for example if the measured moisture content is below a predetermined threshold.

[0035] Yet another broad aspect of the disclosure relates to a system, e.g. a material feed system, the system comprising: a material feed stream passage; a source of treated hygroscopic polymer material for introducing treated hygroscopic polymer material into the material feed stream passage; a source of untreated hygroscopic polymer material for introducing untreated hygroscopic polymer material into the material feed stream passage; a moisture measurement unit for measuring the moisture content of material within the material feed stream passage; and a controller operatively connected to the moisture measurement unit and the source of untreated hygroscopic polymer material; wherein the controller is configured to introduce, in use, untreated hygroscopic polymer material into the feed stream passage if the measured moisture content is below a predetermined threshold.

[0036] The controller may be configured to prevent or suspend the introduction of untreated hygroscopic polymer material into the material feed stream passage, for example if the measured moisture content is above a predetermined threshold, which may be the same further predetermined or may be a further predetermined threshold.

[0037] The predetermined threshold may be a predetermined lower threshold. The further predetermined threshold may be a predetermined upper threshold. The controller may be configured to adjust a quantity, or rate or introduction, of untreated hygroscopic polymer material introduced into the material feed stream passage, for example based on the measured moisture content.

[0038] The controller may be configured to adjust the moisture content of the material within the material feed stream passage, for example by adjusting a rate at which the untreated hygroscopic polymer material is introduced into the material feed stream passage. The controller may be configured to adjust the moisture content of the material within the material feed stream passage based on the measured moisture content.

[0039] The system may comprise or form part of a molding system, e.g. an injection molding system.

[0040] Another broad aspect of the present disclosure provides a molding system, e.g. an injection molding system. The molding system may comprise the material feed system described above.

[0041] Yet another broad aspect of the disclosure relates to a molding system comprising: a material feed stream passage; a source of treated hygroscopic polymer material for introducing treated hygroscopic polymer material into the material feed stream passage; a source of untreated hygroscopic polymer material for introducing untreated hygroscopic polymer material into the material feed stream passage; a moisture measurement unit for measuring the moisture content of material within the material feed stream passage; and a controller operatively connected to the moisture measurement unit and the source of untreated hygroscopic polymer material; wherein the controller is configured to introduce, in use, untreated hygroscopic polymer material into the feed stream passage if the measured moisture content is below a predetermined threshold.

[0042] Hereinafter reference to the system refers to the system, the material feed system or the molding system.

[0043] The system may comprise a molding unit or machine. The molding unit or machine may be operatively connected to the material feed stream passage. The molding unit or machine may be operable or configured to process material introduced thereto from the material feed stream passage. The molding unit or machine may be operable or configured to mold a molded article. The system, molding unit or molding machine may comprise an injection unit. The injection unit may comprise an inlet. The injection unit may be operatively connected to the material feed stream passage. The material feed stream passage may be operatively connected to the inlet of the injection unit. The injection unit may be configured to melt material introduced thereto from the material feed stream passage. The injection unit may be configured to inject, e.g. into a mold, material introduced thereto from the material feed stream passage.

[0044] The system, molding unit or molding machine may comprise a clamp unit. The system, molding unit or molding machine may comprise a mold, which may be receivable by or within the clamp unit. The mold may be configured to describe a molded article.

[0045] The predetermined threshold may be selected or configured to cause, e.g. within the injection unit, hydrolysis in the material introduced into the injection unit from the material feed stream passage. The predetermined threshold may be selected or configured to reduce the intrinsic viscosity of the material introduced into the injection unit from the material feed stream passage.

[0046] The moisture measurement unit may be downstream of a location at which the source of untreated hygroscopic polymer material introduces untreated hygroscopic polymer material into the material feed stream passage. Alternatively, the moisture measurement unit may be upstream of a location at which the source of untreated hygroscopic polymer material introduces untreated hygroscopic polymer material into the material feed stream passage.

[0047] The moisture measurement unit may be upstream of the injection unit, for example the inlet or a barrel of the injection unit, which may include or be operatively connected to the inlet. The barrel may be heated, for example by one or more heaters which may comprise heater bands surrounding the barrel. The injection unit may comprise a screw, for example an extruder screw, which may be received in the barrel. The moisture measurement unit may be incorporated in or operatively connected to the inlet of the injection unit.

[0048] The source of treated hygroscopic polymer material may comprise a dryer, for example a PET dryer. The source of untreated hygroscopic polymer material may comprise dosing unit, for example an undried PET dosing unit. The material feed stream passage or conduit may comprise a pipe or tube, for example at least part of which extends between the sources. The material feed stream passage or conduit may comprise a hopper. The material feed stream passage or conduit may comprise a dosing portion, section or segment. The material feed stream passage or conduit may comprise a moisture measurement portion, section or segment.

[0049] The mold may describe a vial, for example a medical vial such as a blood tube. The molded article may comprise a vial, for example a medical vial such as a blood tube. Alternatively, the mold may describe, or the molded article may comprise, a closure or cap, e.g. a closure cap. The mold may describe, or the molded article may comprise, a container closure or cap, e.g. a container closure cap.

[0050] The controller 5 may be configured to change one or more operating parameters of the injection unit, for example in conjunction with the measured moisture content. The operating parameters may comprise heat power delivered to heaters of the injection unit, screw rotational speed and injection rate. The operating parameters may be changed to generate the desired level of hydrolysis in the material and / or the intrinsic viscosity of the material injected into the mold.

[0051] A further aspect of the invention provides a computer program element comprising computer readable program code means for causing a processor to execute a procedure to implement one or more steps of the aforementioned method.

[0052] A yet further aspect of the invention provides the computer program element embodied on a computer readable medium.

[0053] A yet further aspect of the invention provides a computer readable medium having a program stored thereon, where the program is arranged to make a computer execute a procedure to implement one or more steps of the aforementioned method.

[0054] A yet further aspect of the invention provides a control means or control system or controller comprising the aforementioned computer program element or computer readable medium.

[0055] For purposes of this disclosure, and notwithstanding the above, it is to be understood that any controlled s), control units and / or control modules described herein may each comprise a control unit or computational device having one or more electronic processors. The controller may comprise a single control unit or electronic controller or alternatively different functions of the control of the system or apparatus may be embodied in, or hosted in, different control units or controllers or control modules. As used herein, the terms “control unit” and “controller” will be understood to include both a single control unit or controller and a plurality of control units or controllers collectively operating to provide the required control functionality. A set of instructions could be provided which, when executed, cause said control! erf s) or control unit(s) or control module(s) to implement the control techniques described herein (including the method(s) described herein). The set of instructions may be embedded in one or more electronic processors, or alternatively, may be provided as software to be executed by one or more electronic processor(s).

[0056] For example, a first controller may be implemented in software run on one or more electronic processors, and one or more other controllers may also be implemented in software run on one or more electronic processors, optionally the same one or more processors as the first controller. It will be appreciated, however, that other arrangements are also useful, and therefore, the present invention is not intended to be limited to any particular arrangement. In any event, the set of instructions described herein may be embedded in a computer-readable storage medium (e.g., a non-transitory storage medium) that may comprise any mechanism for storing information in a form readable by a machine or electronic processors / computational device, including, without limitation: a magnetic storage medium (e.g., floppy diskette); optical storage medium (e.g., CD-ROM); magneto optical storage medium; read only memory (ROM); random access memory (RAM); erasable programmable memory (e.g., EPROM ad EEPROM); flash memory; or electrical or other types of medium for storing such information / instructions.

[0057] For the avoidance of doubt, any of the features described herein apply equally to any aspect of the invention. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in any way and / or combination, unless such features are incompatible.

[0058] For the avoidance of doubt, the terms “may”, “and / or”, “e.g.”, “for example” and any similar term as used herein should be interpreted as non-limiting such that any feature so-described need not be present. Indeed, any combination of optional features is expressly envisaged without departing from the scope of the invention, whether or not these are expressly claimed. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner.

[0059] BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:

[0061] FIG. 1 depicts a schematic top view of an injection molding system;

[0062] FIG. 2 depicts a schematic side view of the material feed system and section of the injection unit of the molding system of FIG. 1; and

[0063] FIG. 3 depicts a flow chart of a method of operating the material feed system of FIG. 2.

[0064] DETAILED DESCRIPTION OF THE INVENTION

[0065] With reference to FIGs. 1 and 2, there is depicted a non-limiting embodiment of a molding system 1, which includes a molding machine 2, a mold 3, a material feed system 4 and a controller 5. The molding machine 2 includes an injection unit 20 and a clamp unit 21.

[0066] The injection unit 20 includes an inlet 20a, sometimes referred to as a feedthroat, a barrel 20b, a plurality of heaters 20c, which are heater bands in this example, and a feedscrew 20d received within the barrel 20b. The heaters 20c heat the barrel 20b and material is introduced from the feed system 4 into the inlet 20a of the injection unit 20 and is conveyed and melted along the barrel 20b by rotation of the feedscrew 20d.

[0067] The clamp unit 21 includes a fixed platen 21a and a moving platen 21b, which reciprocates toward and away from the fixed platen 21a in the usual way. The mold 3 is received between the fixed and moving platens 21a, 21b. The fixed platen 21a is operatively connected to the injection unit 20 and includes a hole (not shown) through which molten material is injected by the injection unit 20 into the mold 3. The mold 3 includes a material distributor 30, a cavity plate 31 and a core plate 32. The material distributor 30 is mounted to the fixed platen 21a and is in fluid communication, in use, with the injection unit 20 to receive molten material therefrom. The cavity plate 31 is secured to the material distributor 30 and has a plurality of cavities (not shown) with gates (not shown) through which the molten material is introduced by the material distributor 30 into the cavities (not shown). The core plate 32 is mounted to the moving platen 21b and is moved into and out of mating contact with the cavity plate 31 for molding and demolding articles in the usual way.

[0068] The material feed system 4 includes a source of treated hygroscopic polymer material in the form of a PET dryer 40 in this example. The dryer 40 introduces treated hygroscopic polymer material in the form of dried PET material 40a into a material feed stream passage 41. The material feed stream passage 41 includes a transfer tube 41a connecting the dryer 40 to a hopper 41b. The hopper 41b in turn feeds the dried PET material 40a into a dosing section 41c.

[0069] The material feed system 4 also includes a source of untreated hygroscopic polymer material in the form of a PET dosing unit 42. The dosing unit 42 introduces untreated hygroscopic polymer material in the form of untreated or undried PET material into the dosing section 41c of the material feed stream passage 41. This untreated or undried PET material is combined with the dried PET material in the material feed stream passage 41, prior to its introduction into the inlet 20a of the injection unit 20.

[0070] The material feed system 4 also includes a moisture measurement unit 43 toward the downstream end of the dosing section 41c of the material feed stream passage 41. The moisture measurement unit 43 is upstream of the injection unit 20, but downstream of the dosing unit 42. The moisture measurement unit 43 is configured to measure the moisture content of the combined mixture of the dried PET material and the untreated or undried PET material.

[0071] The controller 5 is operatively connected to the dryer 40, the dosing unit 42 and the moisture measurement unit 43. The controller 5 is configured to cause the dosing unit 42 to regulate the moisture content of the material within the material feed stream passage 41 based on the moisture content measured by the moisture measurement unit 43. In this example, the controller 5 is the central controller of the molding machine 2. However, it will be appreciated by the skilled person that the functionality described herein may be provided by one or more separate or standalone controllers. Such separate or standalone controllers could be operatively connected to the controller 5 of the molding machine 2.

[0072] Referring now to FIG. 3, a molding method 100 is shown which involves adding 101 untreated or undried PET resin into the dryer 40, treating or drying 102 the PET resin and introducing the treated or dried PET resin into the feed stream passage 41. The moisture in the PET resin in the feed stream passage 41 is then measured using the moisture measurement unit 43. The measured moisture content measured by the moisture measurement unit 43 is then compared 105 with a predetermined threshold or range and untreated or undried PET resin is selectively introduced 106 by the dosing unit 42 into the feed stream passage 41 as required to regulate the moisture content.

[0073] More specifically, if the measured moisture content below the predetermined threshold, untreated or undried PET resin is then introduced 106 into the dosing section 41c of the feed stream passage 41. If the measured moisture content is above a predetermined threshold, then no untreated or undried PET resin is introduced and the moisture content is measured continuously.

[0074] Preferably, the quantity of untreated or undried PET resin introduced 106 into the dosing section 41c of the feed stream passage 41 is selectively varied, for example stepwise or varied continuously, based on the moisture content measured. More specifically, the controller 5 is configured to provide infinite or stepwise adjustment of a rate at which the dosing unit 42 introduces untreated or undried PET into the dosing section 41c of the feed stream passage 41 based on the moisture content measured by the moisture measurement unit 43. The controller 5 is thereby able to implement a closed loop control of the moisture content of the material within the material feed stream passage 41.

[0075] The moisture-controlled material feed stream is then introduced into the inlet 20a of the injection unit 20, where it is processed by conveying and melting the material along the barrel 20b via the rotation of the feedscrew 20d. This processing causes hydrolysis in the material, which breaks chemical bonds and shortens the polymer chains and reduces its intrinsic viscosity to that which is required to balance flowability and the mechanical properties of the molded article. The skilled person will appreciate that the amount of hydrolysis that occurs can be controlled tightly by controlling the moisture content as outlined above. However, the controller 5 may also change one or more operating parameters of the molding machine 2 in conjunction with the measured moisture content. For example, the heaters 20c may be operated to vary the temperature of the barrel 20b, one or more operating parameters (e.g. screw rotational speed or injection rate) of the operation of the feedscrew 20d and / or any one or more other operating parameters may be modified to generate the desired level of hydrolysis in the material and / or the intrinsic viscosity of the material injected into the mold 3.

[0076] The mold 3 includes a plurality of cavities (not shown) each of which describes a molded article (not shown). In this example, the molded article (not shown) is a medical vial, specifically a blood tube. The skilled person will appreciate that PET blood tubes have a relatively high flow length to wall thickness (1 / t) ratio and, as such, the fill rate must be sufficient to fill the cavity completely before the flow front solidifies, to avoid underfilling of the cavity. It is also envisaged that the molded article (not shown) could be a container closure. In such cases, the 1 / t ratio in the sealing region can also be problematic.

[0077] In either of these applications, the viscosity of the material is critical as it must balance flowability with the desired mechanical properties of the molded article. In both cases, it is preferable that the intrinsic viscosity of the material is less than 0.7 dl / g, in order to enable an appropriate operating window to fill the cavities adequately. In the case of blood tubes, it is preferable that the intrinsic viscosity of the material is approximately 0.56 dl / g. The skilled person will appreciate that these values of intrinsic viscosity can be present at any stage of the process, but they are preferably present in the PET that is injected into the mold 3.

[0078] It will be appreciated by those skilled in the art that several variations to the construction and / or use of aforementioned examples are envisaged without departing from the scope of the invention. It will also be appreciated by those skilled in the art that any number of combinations of the aforementioned features and / or those shown in the appended drawings provide clear advantages over the prior art and are therefore within the scope of the invention described herein.

Claims

CLAIMS1. A molding method comprising: introducing a treated hygroscopic polymer material into a material feed stream; measuring a moisture content of the material feed stream; and introducing untreated hygroscopic polymer material into the material feed stream if the measured moisture content is below a predetermined threshold.

2. The molding method of claim 1 comprising preventing or suspending the introduction of untreated hygroscopic polymer material into the material feed stream if the measured moisture content is above a predetermined upper threshold.

3. The molding method of claim 1 or claim 2 comprising adjusting the moisture content of the material feed stream by adjusting a rate at which the untreated hygroscopic polymer material is introduced into the material feed stream based on the measured moisture content.

4. The molding method of any preceding claim comprising processing the material feed stream to cause hydrolysis in, and / or to reduce the intrinsic viscosity of, the hygroscopic polymer material in the material feed stream.

5. The molding method of claim 4, wherein the material feed stream comprises a solid resin and processing comprises melting and injecting the solid resin into an injection mold to produce a molded article.

6. The molding method of claim 5, wherein the moisture content is measured downstream of a location at which the untreated hygroscopic polymer material is introduced into the material feed stream.

7. The molding method of claim 6, wherein the material feed stream is operatively connected to an inlet of an injection unit and the moisture content is measured upstream of the inlet.

8. The molding method of any one of claims 5 to 7, wherein the treated hygroscopic polymer material comprises dried polyethylene terephthalate (PET) and the untreated hygroscopic polymer material comprises undried PET having a higher moisture content than the dried PET.

9. The molding method of claims 8, wherein the PET within the material feed stream and / or injected by the injection unit comprises an intrinsic viscosity of less than 0.7 dl / g.

10. The molding method of claim 8 or claim 9, wherein the molded article is a medical vial.

11. The molding method of claim 8 or claim 9, wherein the molded article is a container closure.

12. The molding method of claims 8, wherein the PET within the material feed stream and / or injected by the injection unit comprises an intrinsic viscosity of approximately 0.56 dl / g.

13. A computer program element comprising computer readable program code means for causing a processor to execute a procedure to implement the method of any preceding claim.

14. A computer readable medium having a program stored thereon, where the program is arranged to make a computer execute a procedure to implement the method of any one of claims 1 to 12.

15. A control system comprising the computer readable medium of claim 14.

16. A material feed system comprising: a material feed stream passage; a source of treated hygroscopic polymer material for introducing treated hygroscopic polymer material into the material feed stream passage; a source of untreated hygroscopic polymer material for introducing untreated hygroscopic polymer material into the material feed stream passage; a moisture measurement unit for measuring the moisture content of material within the material feed stream passage; and a controller operatively connected to the moisture measurement unit and the source of untreated hygroscopic polymer material;wherein the controller is configured to introduce, in use, untreated hygroscopic polymer material into the feed stream passage if the measured moisture content is below a predetermined threshold.

17. The material feed system of claim 16, wherein the controller is configured to prevent or suspend the introduction of untreated hygroscopic polymer material into the material feed stream passage if the measured moisture content is above a predetermined upper threshold.

18. The material feed system of claim 16 or claim 17, wherein the controller is configured to adjust the moisture content of the material within the material feed stream passage by adjusting a rate at which the untreated hygroscopic polymer material is introduced into the material feed stream passage based on the measured moisture content.

19. The material feed system of any one of claims 16 to 18, wherein the source of treated hygroscopic polymer material comprises a polyethylene terephthalate (PET) dryer and the source of untreated hygroscopic polymer material comprises an undried PET dosing unit.

20. The material feed system of any one of claims 16 to 18, wherein the moisture measurement unit is downstream of a location at which the source of untreated hygroscopic polymer material introduces untreated hygroscopic polymer material into the material feed stream passage.

21. A molding system comprising the material feed system of any one of claims 16 to 20 and an injection unit configured to melt, and inject into a mold, material introduced thereto from the material feed stream passage, and the predetermined moisture content threshold is configured to cause within the injection unit hydrolysis in, and / or to reduce the intrinsic viscosity of, the material introduced into the injection unit from the material feed stream passage.

22. The molding system of claim 21, wherein the moisture measurement unit is upstream of the injection unit.

23. The molding system of claim 21 or claim 22, wherein the mold describes a medical vial.

24. The molding system of claim 21 or claim 22, wherein the mold describes a container closure.

25. The molding system of any one of claims 21 to 24 comprising a clamp within which the mold is received.

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