This invention relates to polymeric materials and particularly, although not exclusively, relates to apparatus for and a method of dosing a fluid formulation into a polymeric material. Injection moulded products such as container preforms or continuously extruded products such as fibre may be produced.

It is well-known to dose fluid formulations, for example liquid formulations comprising colour and/or functional additives such as UV blockers, into thermoplastic polymeric materials to produce injection moulded or extruded products. However, it is difficult to confirm dosing systems are functioning with appropriate accuracy and/or ensuring that the correct amount (not too little or too much) of the liquid formulation is dosed into the polymeric material. For example, it is desirable for beverage bottle manufacturers to have certaincy on the levels of additives (e.g. colourants) included in bottles produced. When a bottle or other receptacle is intended to include a functional additive at a specific level, such as a UV light blocker to prevent deterioration of product contained in the receptacle, it is important to have confidence, from a quality assurance perspective, that the receptacle contains the appropriate amount of the functional additive. Many receptacles are made from preforms produced by injection moulding in an injection moulding machine. The preforms are then left for a period of time to condition them prior to blowing and stretching them on a stretch blow-moulding machine. Receptacles produced may then be periodically sampled and assessed. For example, the colour of a selected receptacle may be assessed and the level of any functional additive may be assessed, insofar as this is possible. In some cases, it may not be readily possible or convenient to assess the level of certain functional additives in blown receptacles in which case it is difficult for a manufacturer of the receptacles to provide a reliable quality assurance (QA) process for such receptacles at least as regards such a functional additive. In a case wherein colour of a receptacle or the level of functional additive in the receptacle is assessed as a QA process, it should be appreciated that such assessment is undertaken far downstream of a point wherein the colour or functional additive is introduced into a preform which is subsequently stretch blow-moulded to define the receptacle. If the QA assessment shows a receptacle is defective in some way, then all receptacles produced in the period between production of the preform for the defective receptacle and the time when the receptacle is found to be defective must also be presumed to be defective (or will need to be subjected to rigorous testing) and may need to be discarded. Given that it could easily be more than one hour between production of a preform and the assessment of a receptacle produced from it and given that, typically, receptacles are produced at high speed (e.g. 15000 per hour), then tens of thousands of defective receptacles may be produced which need to be discarded.

In a case wherein it is not readily possible or convenient to assess the level of a particular functional additive included in a preform or receptacle, production of a defective receptacle (e.g. containing too little additive) may be even more serious, since the receptacle may be filled with product without assessing the additive level, and sold to customers. The defective receptacle (e.g. having too little of a functional additive such as a UV blocker) may not sufficiently protect the product it contains, thereby reducing its shelf life. The existence of such a product with reduced shelf life may necessitate the recall of many tens of thousands of product-containing receptacles with significant loss to retailers, the manufacturer of the product contained in the receptacle and/or the receptacle manufacturer.

It is an object of the invention, in one preferred embodiment, to address the above described problems and provide an accurate QA system which is able to relatively quickly provide an alert in the event that a defective preform and/or receptacle may be produced.

US7958915 addresses the problem of maintaining a desired rate of liquid colour delivery in producing plastics parts, in order to prevent overuse of colouring agents in the production of the parts. The problem is solved by providing a liquid colour gravimetric metering apparatus. The apparatus includes a scale for continuously measuring the weight of a container of liquid colour concentrate in the course of pumping liquid colour therefrom into a plastics material, a pump for pumping the liquid colour concentrate and a controller for continuously comparing the measured weight of the liquid colour concentrate to an expected weight of the container of liquid colour concentrate based on a desired usage rate of liquid colour concentrate. The speed of the pump is adjusted continuously in response to the measured weight of the container of liquid colour concentrate compared to the expected weight of the container of liquid colour concentrate, thereby to supply continuously the desired amount of liquid colour concentrate to the plastics material. However, disadvantageously, Applicant has found that gravimetric measurement of liquid colour concentrate tends to be of low accuracy and using an inaccurately determined parameter (i.e. measured weight of liquid colour concentrate) to continuously adjust a pump which delivers the liquid colour concentrate into plastics material results in low certaincy of the amount of liquid colour concentrate actually dosed into a polymeric material in a melt processing apparatus.

It is an object of a preferred embodiment of the present invention to address the above described problem. It is an object of preferred embodiments of the present invention to provide an apparatus and/or method for confirming on a substantially continuous basis that apparatus for dosing a liquid colour formulation into a polymeric material is functioning with appropriate accuracy. According to a first aspect of the invention, there is provided apparatus for dosing a fluid formulation into a polymeric material, the apparatus comprising: a receptacle (A) for containing a fluid formulation;

a pump (A) for pumping fluid formulation away from said receptacle (A); and

a level sensor for measuring the level of fluid in the receptacle (A).

Said receptacle (A) may have a total internal volume (i.e. brim full) of at least 2 litres or at least 3 litres for containing a fluid formulation. The total internal volume may be less than 50 litres or less than 20 litres.

Said receptacle (A) may have a substantially constant internal cross-sectional area over a length L, wherein L is at least 50mm, preferably at least 100mm. Length L may be less than 400mm or less than 200mm. The volume of fluid which can be contained within said substantially constant cross-sectional area may be at least 500cm ³ , preferably at least 1000cm ³ . It may be less than 20000cm ³ , less than 10000cm ³ or less than 7000cm ³ .

Said substantially constant internal cross-sectional area may at least 100cm ² , preferably at least 200cm ² . It may be less than 2000cm ² , less than 1000cm ² or less than 600cm ² . The said substantially constant internal cross-section is preferably curved along its entire extent; preferably it is circular or oval-shaped.

The ratio of the substantially constant internal cross-sectional area divided by the total internal volume of the receptacle (A) may be in the range 0.01 -0.20, preferably in the range 0.02-0.14, more preferably in the range 0.03-0.10.

Said receptacle (A) preferably includes a base on which it is seated and/or which extends horizontally. Said substantially constant internal cross-sectional area preferably extends substantially parallel to said base. Length L is preferably measured substantially perpendicular to the base.

Said receptacle (A) is preferably rigid. It is preferably self-supporting. It is preferably not arranged to be compressed to deliver fluid formulation therefrom. Its internal volume is preferably not arranged to change (e.g. reduce) during removal of fluid formulation therefrom. Said receptacle (A) suitably has an inlet for input of the fluid formulation into the receptacle. Said inlet is preferably positioned in an upper part of the receptacle (A). It is preferably positioned above a maximum fill level of receptacle (A), wherein data on said maximum fill level (e.g. its position) is stored in a computer which is suitably a component of said apparatus.

Said receptacle (A) is suitably in fluid communication with a receptacle (B) which is suitably arranged to contain the same fluid formulation as contained in receptacle (A) and the apparatus is suitably arranged for fluid from receptacle (B) to be transferred to receptacle (A) to replenish fluid in receptacle (A). A tube preferably extends between receptacle (A) and receptacle (B) for transferring fluid formulation from receptacle (B) to receptacle (A), Said tube may have an internal diameter in the range 0.5 to 3cm. A pump (B) is preferably provided for pumping fluid from receptacle (B) to receptacle (A). Receptacle (B) preferably has a greater total internal volume than receptacle (A). The ratio of the total internal volume of receptacle (B) divided by the total internal volume of receptacle (A) may be at least 1 .5, for example in the range 1 to 500 or, preferably 1 .5 to 10

Receptacle (B) may be collapsible. It may comprise a cardboard box which encloses a plastics receptacle. It may comprise a bag-in-a-box arrangement.

Said receptacle (A) preferably includes an outlet for the fluid formulation. Said outlet is preferably positioned in a lower part of the receptacle (A). It may be positioned at or adjacent an internal base wall of said receptacle (A). Said internal base wall may be an internal wall of receptacle (A) which faces in an opposite direction to the base on which receptacle (A) is seated. Said outlet may extend through a said base of receptacle (A) on which receptacle (A) is seated and/or which extends horizontally.

Said pump (A) is preferably arranged to pump fluid formulation away from said receptacle (A) for example away from said outlet of said receptacle (A). A first tube preferably extends between said receptacle (A), for example the outlet thereof, and said pump (A).

Said level sensor is preferably non-invasive. It is preferably arranged so that it does not contact fluid formulation in receptacle (A) whilst taking a measurement, for example whilst sensing the level of fluid formulation in receptacle (A). Said level sensor preferably includes a transmitter for transmitting a signal, for example a wave. Said signal is suitably arranged to be transmitted towards fluid in receptacle (A), preferably towards an interface of the fluid with air— that is, the wave is suitably arranged to be transmitted so it impinges the top of fluid formulation contained within receptacle (A), suitably to facilitate determination of the level of fluid formulation in receptacle (A). Said level sensor preferably includes a receiver for receiving a signal, for example a wave, reflected from fluid formulation in the receptacle (A). Said level sensor and/or a computer associated therewith is suitably arranged to assess the level of fluid formulation in the receptacle (A) from said transmitted and reflected signals, for example waves.

Said transmitter and said receiver of said level sensor are preferably fixed in position relative to one another and/or are fixed to the same housing. Said housing may be releasably securable to receptacle (A). Said level sensor, for example said housing, is preferably mounted so it occupies a positon which, in use, is above fluid formulation in receptacle (A). Said level sensor is preferably mounted on an upper part of said receptacle (A).

Said level sensor is preferably arranged to transmit a signal, for example a wave. Said level sensor is preferably arranged to transit said signal, for example wave, at greater than 15000Hz, for example greater than 20,000Hz. Said level sensor is preferably arranged to transmit (and suitably receive) an ultrasonic wave. Said level sensor is preferably an ultrasonic sensor. It suitably comprises a housing which houses both an ultrasonic transmitter and ultrasonic receiver.

Preferably, said level sensor, for example ultrasonic sensor, is arranged to produce an analogue output. The operating range of the sensor may be up to 350mm, typically 30 to 250mm, suitably as measured from a transmitting face of the sensor. A computer of said apparatus is suitably programmed so that receptacle (A) is filled with fluid formulation to a level which is spaced a distance of at least 30mm from a transmitting face of the level sensor.

Said level sensor is preferably arranged to communicate level information to a or said computer which is suitably part of said apparatus.

Said pump (A) may be a positive displacement pump, a progressing cavity pump (pep) or other type of positive displacement pump suitable for metering a liquid additive such as a peristaltic pump. It is preferably a pep.

Said receptacle (A) is suitably upstream of the pump (A) with the receptacle (A) being directly connected to the first pump via a first tube, as described. The first tube preferably provides an uninterrupted fluid connection between receptacle (A) and pump (A). The receptacle (A) is preferably arranged to deliver fluid formulation to the inlet of the pump (A) at a pressure of less than 1 .5 bar. Said receptacle (A) is preferably open to the atmosphere. Advantageously, it is preferably not pressurized. Suitably, the apparatus is arranged such that the pressure at the inlet of pump (A) is defined by the static head of fluid in the receptacle (A) and atmospheric pressure and no additional means is provided for pressurizing the receptacle (A). Preferably, the receptacle (A) and pump (A) are arranged for flooded suction of pump (A) with fluid from the receptacle (A).

When said pump (A) is a pep, as is preferred, said pep may include 2 to 20 cavities, preferably 2 to 10 cavities, more preferably 3 to 8 cavities. The cavities may have volumes in the range 0.05ml to 1 .2ml, for example in the range 0.06ml to 0.9ml. Said pep suitably includes a rotor/stator assembly which includes an elastomeric stator, for example a rubber (e.g. nitrile rubber) stator. It may include a metal, for example steel (e.g. stainless or chrome plated) rotor. In a first embodiment, pump (A) may be arranged to pump fluid formulation to an outlet of the apparatus. In this case, preferably, the only pump provided between an outlet of said receptacle (A) and an outlet of said apparatus is said pump (A). Such an arrangement may be used to introduce liquid formulation into polymeric material (for example polymeric material which is not molten and/or is at ambient pressure) at relatively low pressure. In this case, the outlet of said apparatus may be arranged to deliver fluid formulation onto solid pellets of polymeric material. The solid pellets may be upstream of a melting zone of a melt-processing apparatus with which the apparatus for dosing may be associated and/or operatively connected.

In a second embodiment, said apparatus may be arranged to introduce liquid formulation into polymeric material (for example polymeric material which is molten) at relatively high pressure (e.g. at greater than 50 bar). In this case, an outlet of said apparatus may be arranged to deliver fluid formulation into molten polymer in a melt-processing apparatus (e.g. injection moulding machine or extruder). The apparatus for dosing may be associated with and/or operatively connected to a melt-processing apparatus as described.

In order to introduce liquid formulation at relatively high pressure as described in the second embodiment, said apparatus may include a pump (C) downstream of pump (A) and suitably upstream of an outlet of said apparatus. Said pump (C) is preferably arranged to increase the pressure of the liquid formulation. Said pump (C) is suitably arranged to increase pressure by at least 10000KPa (100 bar), more preferably by at least 15000KPa (150 bar), especially by at least 19000KPa (190 bar). Said pump (C) may include at least 10 or at least 20 cavities. Suitably it includes fewer than 96 cavities. Preferably, said apparatus for dosing is operatively connected to a melt-processing apparatus, suitably so an outlet of the apparatus is arranged to deliver fluid formulation from said apparatus to polymeric material arranged to be melt-processed in said melt-processing apparatus. Said melt-processing apparatus may comprise an injection moulding machine or extruder.

Said apparatus, for example said receptacle (A) and pump (A) and preferably receptacle (B), when provided, may be mounted on a transportation vehicle. Preferably, the transportation vehicle supports receptacles (A) and (B) which contain liquid formulation. The transportation vehicle may be arranged to be rolled to a position in which it is to be used, for example a position adjacent a melt-processing apparatus. The transportation vehicle may include wheels or rollers (e.g. at least three, preferably at least four wheels or rollers). A computer, suitably arranged to control operation of pump (A) and to receive data from the level sensor, is preferably a component of the transportation vehicle. The vehicle preferably has a height of less than 1 .8m. The footprint of the vehicle may be less than 2m ² or less than 1 m ^2; and it may be at least 0.2m ² .

Unless otherwise stated, viscosity described herein may be measured using a Brookfield Viscometer at 20 rpm and 23 °C.

Said fluid formulation may have a viscosity of at least 5000cP, suitably at least l OOOOcP, preferably at least 15000cP. The viscosity may be less than 45,000cP, preferably less than 40,000cP, more preferably less than 35,000cP. Said fluid formulation may include at least 20 wt%, suitably at least 30 wt%, preferably at least 40 wt%, more preferably at least 50 wt%, especially at least 60 wt%, solids. Said solids may comprise particulate material, for example solid pigments and/or dyes. Said fluid formulation may include 85 wt% or less of solids of the type described. Said fluid formulation suitably includes 15 to 70 wt%, preferably 15 to 50 wt% of fluid, for example liquid. Said solids are suitably provided as a dispersion in a fluid which is suitably a vehicle. Thus, the solids may be generally insoluble in the vehicle. The ability to use highly loaded formulations (and consequently relatively low vehicle levels) may be advantageous in minimizing any detrimental effect associated with incorporation of vehicle into the polymeric material. Said solids may be arranged to adjust a property of a plastics material into which they may be delivered by the apparatus. Said solids may comprise any material that it is desired to introduce into a plastics material and may be selected from colourants, UV filters, oxygen absorbers, antimicrobial agents, acetaldehyde scavengers, reheat additives, antioxidants, light stabilizers, optical brighteners, processing stabilizers and flame retardants. Colourants may comprise pigments or dyes.

Said solids preferably comprise insoluble colourants (i.e. insoluble in the vehicle), for example insoluble pigments or dyes. In some embodiments, partially soluble colourants or other additives may be used.

Said vehicle is suitably a liquid at STP. Said fluid formulation is preferably a liquid at STP. Said vehicle preferably has a boiling point (at atmospheric pressure of 760mmHg) of greater than 300°C, preferably greater than 350°C, more preferably greater than 500 °C. The boiling point may be less than 1 150°C or less than 1000°C.

Said receptacle (A) preferably contains a fluid formulation as described. Receptacle (B), when provided, suitably includes a fluid formulation, with the fluid formulation in receptacles (A) and (B) being identical. The apparatus is suitably arranged to deliver fluid formulation from receptacle (A) so it contacts polymeric material, wherein the fluid formulation which contacts the polymeric material is identical to the fluid formulation in receptacle (A).

According to a second aspect of the invention, there is provided a method of dosing a fluid formulation into a polymeric material, the method comprising:

(i) pumping a fluid formulation away from a receptacle (A) and towards a polymeric material;

(ii) assessing, for example measuring, the level of fluid in receptacle (A) during step (i); and

(iii) dosing the fluid formulation into a polymeric material.

Said fluid formulation may have any feature of the fluid formulation of the first aspect.

Said receptacle (A) may have any feature of receptacle (A) of the first aspect.

The level of fluid in receptacle (A) may be measured by a level sensor having any feature of the level sensor of the first aspect.

A pump (A) preferably pumps fluid formulation as described in (i). The method may utilise one or more other pumps, for example as described in the first aspect, to facilitate passaged of fluid formulation between receptacle (A) and said polymeric material. Said method preferably includes communication of data collected in step (ii) to a computer. The computer may include any feature of the computer of the first aspect.

Said method preferably uses a level sensor as described and said computer may control operation of and/or receive data from said level sensor in the method.

Said computer may control operation of and/or receive data from pump (A) in the method.

Said polymeric material of step (iii) is preferably melt-processed by a melt-processing apparatus in the method. For example, it may be injection moulded or extruded. Said computer preferably communicates with said melt-processing apparatus in the method. Data is preferably sent from melt-processing apparatus to said computer in the method.

Said method preferably comprises an operator selecting a parameter relating to an amount of liquid formulation to be dosed in step (iii) of the method. The amount may be defined as a let-down-ratio (LDR). In the method, a metering device, for example a metering pump, may be arranged to deliver a metered amount (e.g. amount per unit time) of liquid formulation into said polymeric material. Pump (A) described herein is preferably said metering pump.

Said computer is preferably programmed to calculate the volume and/or weight of fluid formulation pumped away from receptacle (A) in step (i) based on a change in the level of fluid in receptacle (A) measured as described in step (ii), preferably by said level sensor. Said computer is preferably programmed to calculate the rate of passage of fluid formulation away from receptacle (A) in step (i) based on a change in the level of fluid in receptacle (A) measured as described in step (ii),

Said method preferably comprises comparing (e.g. a computer comparing) said rate of passage of fluid formulation based on a change in the level of fluid in receptacle (A) (preferably based on measurements from said level sensor) with an amount, for example rate, of fluid formulation arranged to be delivered by said metering device, for example metering pump described. If, in the comparison, an amount assessed based on data from said level sensor and an amount based on said metering device differ by more than a predetermined amount then said computer will arrange for a signal to be output, for example an alarm sounded, to alert an operator to the discrepancy and/or possible malfunctioning of some aspect of the apparatus. The operator may then investigate the reason for the discrepancy.

In one preferred embodiment, when step (iii) of the method comprises a cyclic process (e.g. injection moulding of preforms) the method comprise the computer calculating data relating to the amount (e.g. weight) of liquid formulation introduced into the polymeric material per cycle, based on data communicated to the computer from said level sensor. The data is suitably compared, by the computer, with data from said metering pump (e.g. number of turns of the metering pump) which is arranged to meter liquid formulation into said polymeric material in step (iii). If a comparison of data from the level sensor and from the metering pump suggests an inconsistency, a signal (e.g. alarm) is output as described.

In one preferred embodiment, when step (iii) of the method comprises a continuous process (e.g. extrusion of fibre), the computer may be arranged to compare data from the level sensor and data from said metering pump periodically, for example every time the level of liquid formulation in receptacle (A) falls a predetermined amount (e.g. 1 mm).

The method may comprise an operator selecting a parameter relating to the amount of said fluid formulation to be dosed into the said polymeric material and inputting information relating to said parameter into a computer which controls operation of the apparatus to dose said formulation into said polymeric material in accordance with said parameter. Said parameter may relate to a desired dose rate of said fluid formulation into said polymeric material.

The method may comprise an operation inputting, into said computer, information on throughput of said polymeric material, for example on cyclic or continuous (e.g. hourly) throughput.

Preferably, after contact between said formulation and said polymeric material, the mixture includes less than 15 wt% (for example less than 10 wt%) of material derived from said formulation and greater than 85 wt% (for example greater than 90 wt%) of polymeric material with which the formulation is contacted in the method.

Preferably, formulation is selected and dosed at a rate which introduces less than 15wt%, more preferably less than 10wt%, or less than 8wt% of vehicle into the polymeric material. That is, after contact between formulation and polymeric material, the amount of vehicle in the mixture is preferably less than 15wt%, less than 10wt% or less than 8wt%. Preferably, after contact between formulation and melted polymeric material, the sum of the amounts of all liquids introduced into the polymeric material via said formulation is less than 15wt%, less than 10wt% or less than 8wt%, based on the total weight of mixture comprising said formulation and said polymeric material after said contact.

Said polymeric material may be selected from polyesters (especially PET), polycarbonates, polyolefins, PVC, fluoropolymers and other engineering polymers. Said polymeric material is preferably a polyester, more preferably PET. Downstream of contact between said formulation and said polymeric material, the mixture may be used to form sheet or fibre; or injection moulded articles, for example preforms for receptacles. The method may include a preliminary process which suitably precedes step (iii) and may be carried out a single time for a said fluid formulation which is to be dosed in the process. The preliminary process suitably comprises determining the specific gravity of said fluid formulation, suitably using the apparatus of the first aspect. Thus in a third aspect, there is provided a method of determining the specific gravity of a fluid formulation associated with an apparatus according to the first aspect, the method comprising:

(a) selecting apparatus of the first aspect;

(b) operating pump (A) to pump fluid formulation away from receptacle (A);

(c) using said level sensor of the apparatus to monitor the change in level of said liquid formulation in the receptacle (A);

(d) a computer of said apparatus calculating the volume of liquid formulation removed from said receptacle (A) over a known time, based on data from step (c);

(e) calculating the specific gravity by dividing a value of weight displaced per revolution of pump (A) over said known time by the volume determined in step (d).

The value of weight displaced per revolution of pump (A) referred to in step (e) may be determined by:

(i) operating pump (A) for a known period of time;

(ii) collecting the fluid pumped away from receptacle (A) during the period of time and weighing it; and

(iii) recording data relating to the number of revolutions of pump (A) during the period of time. The weight displaced per pump revolution can then be calculated. The invention extends to the use of apparatus of the first aspect for injecting a fluid formulation into a polymeric material.

Any feature of any aspect of any invention or embodiment described herein may be combined with any feature of any aspect of any other invention or embodiment herein mutatis mutandis.

Specific embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic representation of a dosing apparatus;

Figure 2 is a front view of a dosing apparatus; Figure 3 is a rear view of the dosing apparatus of Figure 2;

Figure 4 is a schematic side view, partly in cross-section of a receptacle which incorporates a level sensor; Figure 5 is a schematic representation of an optional part of the dosing apparatus which may be positioned downstream of the apparatus of Figures 1 to 3;

Figure 6 is a graph representing shot weight variation in grams over 50 moulding machine cycles starting at a first time and comparing a calculated shot weight from a dosing ratio input by an operator, a shot weight determined using a level sensor and a shot weight determined using a load cell; and

Figure 7 is a graph as for Figure 6 but taken at a later time and being represented on a different scale.

In the figures, the same or similar parts are annotated with the same reference numerals.

Referring to Figure 1 , in general terms, apparatus 2 for dosing a liquid colour formulation, optionally including other additives, into polymer includes a first receptacle 4 for the liquid colour formulation, a progressing cavity pump 6 downstream of the receptacle for pumping the formulation along tube 8 towards an outlet 10. Pressure sensor 12 monitors pressure in tube 8. A level sensor 16 is associated with the top of receptacle 4 and is arranged to monitor the level of liquid in the receptacle 4 and communicate data to a computer in the form of a programmable logic controller (PLC).

In order to allow the change in level of liquid in receptacle 4 to be converted to a volume (and later a weight) of liquid as hereinafter described, the receptacle 4 has a constant internal cross-sectional area across a significant part of the height of the receptacle. Referring to Figure 4, receptacle 4 includes region 200 of constant internal cross-sectional area, in which level sensor 16 is arranged to take measurements. Region A is positioned distance D1 from an emitting face of level sensor 16 and extends to position which is a distance D2 from the emitting face. For any receptacle 4 used in the apparatus, the distance over which the internal cross- sectional area is constant is known (as is the magnitude of the actual area), for example by virtue of having been empirically determined and this distance defines, at its extremes, the upper and lower boundaries for measurement by the level sensor. That is, the level sensor is suitably not arranged to measure liquid level unless the level of liquid is within the area of constant internal cross-section of the receptacle. Data relating to the boundaries is suitably stored in the PLC which is suitably programmed so that the liquid level is only measured when the level is within the boundaries as aforesaid.

Characteristics of receptacles 4 which may be used may be as follows:

Referring to Figures 2 and 3, the apparatus is shown mounted on a cart 20 which includes a platform 22 and associated structures supported on four wheels 24.

The cart 20 includes a platform 26 on which a second receptacle 28 is removably supported. The receptacle 28 is a bag-in-a-box receptacle and is a storage receptacle for colour formulation which is arranged to periodically be fed, via pipes 30, 31 and a peristaltic (or eccentric screw) pump 32 into the first receptacle 4 to replenish the amount of liquid formulation in receptacle 4. Transfer of liquid formulation from receptacle 28 may be commenced when the level of liquid formulation in the first receptacle 4 falls below a predetermined level.

Level sensor 16 is fitted to the top of receptacle 4 and is arranged to measure the distance to the top of the liquid in the receptacle 4 substantially continuously. In a preferred embodiment, level sensor 16 is an ultrasonic level sensor which involves measurement of the time it takes for a sound wave emitted by the sensor to return from the surface of the liquid in the receptacle 4. The distance can be related to the volume of liquid used over time and converted to a weight of liquid used over time as hereinafter described. Control of sensor 16 and data therefrom is fed via lead 34 to the PLC 36.

An ultrasonic level sensor is found to be particularly advantageous for use with a range of formulations (e.g. of varying viscosities, coloured or non-coloured, clear, opaque or semi- opaque) which it may be desired to introduce into polymers. Furthermore, it is found that use of an ultrasonic level sensor, in combination with the relatively viscous formulations which are preferably delivered using the apparatus, allows relatively accurate and stable measurement of the level of liquid formulation in receptacle 4 over time, even if apparatus 2 is inadvertently knocked by an operator or is subjected to another outside source.

A pipe 38 communicates with a lower end of receptacle 4 and extends to a lower end of the pump 6.

Pump 6 may be any type of pump which can accurately meter the liquid formulation delivered by the apparatus. In Figure 3, it is shown as a progressing cavity pump (pep). A suitable pep may be relatively lightweight and have a discharge capacity of 2 or 3 bar. It may include 4 or 6 cavities of substantially identical volume which may be in the range 0.08ml to 2.6ml. The speed of the pump may be controlled by the PLC during the method. An outlet end 40 of the pump communicates with tube 8 which may be arranged to deliver accurately metered quantities of the liquid colour formulation into or onto polymer.

In a first embodiment, tube 8 may be positioned to deliver liquid formulation into or onto solid polymer pellets which are associated with a melt-processing apparatus but are upstream of a melting zone thereof. In this case, the liquid formulation may be dosed at relatively low pressure (e.g. less than 5 bar) onto the polymer pellets.

In a second embodiment, represented in Figure 4, tube 8 may deliver liquid formulation into an inlet of a gear pump 42. Pressure transducer 12 upstream of pump 42 measures the pressure in tube 8. Downstream of the gear pump 42 is a pressure sensor 48 and pressure regulator 51 . The gear pump is driven by a servo motor and is arranged to boost pressure of the liquid formulation so it can be injected directly into a stream of melted polymer in a melt- processing apparatus. The gear pump may be used to increase pressure to more than 100 bar or more than 150 bar. Apparatus which includes a metering pump and a pressure increasing pump which may be used with the apparatus of Figures 1 to 3 is described in WO2014207472.

As an alternative to the provision of a gear pump as a pressure raising pump in the second embodiment, the gear pump may be replaced with a pep which is arranged to increase pressure of the liquid formulation as described in GB1516143.3.

The PLC 36 is arranged to communicate with and control components of apparatus 2 and to communicate with melt processing apparatus, for example as injection moulding machine or extruder, into which liquid formulation may be introduced in the method. The PLC includes a touch screen 42 for inputting and for outputting information. Information which may be input includes data on the pressure of the polymeric material (especially when liquid formulation is injected into molten polymer),the throughput of an associated melt-processing apparatus, a start signal from an injection molding machine or a run signal in the case of continuous extrusion. When the apparatus 2 is operated, it creates a pressure due to the resistance and friction in the tube 8. The pressure sensor 12 fitted adjacent the pump outlet records the pressure each cycle (or, when the apparatus is used to continuously deliver liquid formulation into or onto polymer such as during continuous production of fibre, pressure is recorded periodically, for example every 30 seconds) to ensure it falls within predetermined parameters.

In use, the PLC controller is programmed so that, if it receives a start signal (e.g. manually input by an operator or produced automatically when introduction of liquid formulation into a melt-processing apparatus is commenced), it takes the current liquid level in receptacle 4 and the time of the measurement as datum points. The PLC controller may also take a current liquid level in receptacle 4 as a datum point in the following circumstances:

(i) When it perceives a change in the let-down ration (LDR), for example due to a change in a parameter which leads to a change in pump speed. (ii) When it perceives a change in polymer throughput (which may be altered manually or can be monitored and automatically changed).

(iii) When 1 mm of liquid formulation has been used as measured by level sensor 16. In the following, Example 1 describes how pump 6 is calibrated; Example 2 describes how the dosing apparatus can be calibrated to allow the weight of liquid formulation per unit time to be output (in addition to or instead of a volume of liquid formulation used per unit time, which may be calculated directly from the distance measured by the level sensor 16 provided the relevant cross-sectional area of the first receptacle 4 is known); Example 3 describes how the amount of liquid formulation delivered may be reported; Example 4 describes how the apparatus may be operated to confirm that dosing into molten polymer is at the accuracy level required; and Example 5 is a comparative example which assesses dosing accuracy by use of a shear beam load cell. Example 1 - Calibration of pump

The pump 6 is inherently able to reliably deliver an accurate dose of liquid formulation per revolution. Accuracy is typically over 98%. The weight displacement per pump revolution is calculated by running the pump for a predefined period (which may be defined by a user but typically may be up to 300 seconds), collecting the discharge in a container and recording the number of pump revolutions during delivery of liquid formulation into the container. The liquid in the container is then weighed and data entered into the PLC which then calculates a value for the grams per pump revolution. This value is used in subsequent calculations.

Example 2 - Calibration of apparatus to allow weight of liquid formulation to be reported With a liquid colour formulation to be dosed into polymer associated with a melt- processing apparatus contained in the receptacle 4, the apparatus 2 is operated to pass the formulation through the apparatus and out of outlet 10. The following steps are undertaken:

(i) The level sensor 16 assesses when a fixed amount (e.g. 1 mm) of liquid has been used from receptacle 4.

(ii) The distance the level of liquid has fallen in the receptacle (i.e. 1 mm) is then multiplied by the surface area calculation for the selected reservoir which is based on the known internal cross-sectional area for the reservoir, to yield a resultant volume.

(iii) The resultant volume calculated is then divided by the number of pump revolutions that occurred during the time taken to use the volume of liquid, yielding a millilitres per pump revolution value. (iv) The specific gravity is calculated by dividing the grams per revolution (determined as described in Example 1) by the millilitres per revolution value.

Having determined the specific gravity, the weight of liquid formulation delivered from the receptacle 4 over time can be reported based on the change in height of liquid in the receptacle as measured by the level sensor 16. As will be appreciated, the weight per unit time equals the volume over unit time multiplied by the specific gravity; and the volume equals the change in height of liquid in the receptacle multiplied by the surface area.

Example 3 - Reporting amounts of liquid formulation delivered into a process

Given the weight of the liquid formulation delivered from the receptacle 2 can be determined as described in Example 2 and on the presumption all such formulation is delivered into polymer associated with a melt-processing apparatus downstream of outlet 10, detail on the weight of liquid formulation (and the amount of each component of the liquid formulation) can be used as follows:

(i) If the melt-processing apparatus (e.g. injection moulding machine) is running in a cyclic process, the weight of liquid formulation (or for example the weight of colorant) introduced per cycle may be calculated. In this regard, the weight used for every 1 mm fall in the level of liquid in the receptacle is known from the Example 2 calculation and data is stored in the PLC. The PLC also includes data relating to the number of revolutions of the pump which will take place for every 1 mm fall in the level of liquid in the receptacle if the pump and level sensor are functioning correctly. During the cyclic running of the melt-processing apparatus, data relating to the number of turns of the pump per cycle is monitored and recorded by the PLC. From the aforementioned, the PLC calculates, based on the change in the height of liquid in the receptacle (as assessed by the level sensor), how much liquid has been introduced into the polymer per cycle.

(ii) If the melt-processing apparatus is running a continuous process (e.g. extrusion of fibre), the calculated weight can be used to yield the consumption level of liquid formulation in grams/hour; with this being reported by the PLC for every 1 mm fall in the level of liquid in the receptacle.

In both cases (i) and (ii), if the amount of liquid formulation intended to be delivered by the pump (as programmed in the PLC) per cycle (in the case of the discontinuous process (i)) or per 30 seconds (in the case of the continuous process (ii)) differs by more than a predetermined amount (the level of which may be set by an operator) from the amount delivered per cycle or per 30 seconds (as applicable) as calculated based on measurements by the level sensor, then an alarm is sounded to alert an operator to the discrepancy. The operator may then stop the process and investigate. It should be appreciated that a discrepancy in liquid formulation delivered is reported rapidly (e.g. within about 1 cycle or 30 seconds) meaning that, if there is a problem and products are produced with an incorrect level of liquid formulation (meaning the levels of colourant and/or other additives are incorrect) then a minimum level of defective products will be produced before the situation can be assessed and resolved.

It should be noted that data from the level sensor is not used to adjust the speed of the pump automatically. As described an alarm is sounded and it is left for the operator to investigate the reason for any discrepancy. This is because the pump used as described is inherently highly accurate and it is not believed to be appropriate to adjust the pump speed based on data from the level sensor which cannot be regarded as any more accurate than the pump itself. Any discrepancy described could be due to any of multiple reasons (e.g. defective pump, defective level sensor, a leak or a blockage). Example 4 - Operation of the apparatus and construction of graph confirming shot weight of liguid formulation over time The apparatus of Figures 1 to 3 was set up to meter liguid formulation into polymer in an injection moulding machine arranged to produce 72 x 25.5g PET preforms, per cycle. An operator has the facility, via the PLC, to input and/or adjust LDR, polymer shot weight or throughput, high and low liguid levels for receptacle 4 (the low liguid level determines when receptacle 4 is replenished from receptacle 28) and input details on the size etc. of receptacle 4 (thereby to enable volume of liguid dispensed to be calculated based on data from the level sensor).

During the dosing process, data such as from the level sensor 16, is sent to the PLC controller and a continuous real-time graph of shot weight (of liguid formulation into each preform) per cycle is produced, as illustrated in Figures 6 and 7, a discussion of which is provided hereinafter.

If during operation of the apparatus, liguid formulation from receptacle 28 is transferred to receptacle 4 to replenish it, the PLC is programmed so no alarm is sounded during such transfer. After the transfer, a datum point representing the new level of liguid formulation in receptacle 4 is taken and the operation of the apparatus continues as previously.

Example 5 - Operation of apparatus which includes load cell to assess shot weight (Comparative Example)

The apparatus of Figures 1 to 3 was modified to include, in addition to the level sensor 16, a shear beam load cell fitted below the receptacle 4 which was arranged to measure the weight of the receptacle over time and communicate information to the PLC controller. The PLC records the weight to the nearest 0.1 g and subtracts the weight from a previously recorded weight to yield a shot weight for a cycle.

The level sensor 16 and load cell were operated concurrently, in the comparative example, to enable a comparison of the outputs as illustrated in Figures 6 and 7. Discussion of Figures 6 and 7

The figures record data obtained when concurrently operating a level sensor of Figures 1 to 3 and load cell as described in Example 5. Line A indicates the calculated gram/cycle determined by a dosing weight inputted into the PLC by an operator, line B indicates the gram/cycle assessed by the level sensor and line C indicates the gram/cycle assessed by the load cell. Figures 6 and 7 clearly illustrate the advantages in using the level sensor compared to the load cell. More particularly, the accuracy of use of the load cell is relatively low and results in the reporting of large weight variances over time (which do not represent the true situation). As a result, if a load cell was used to operate an alarm in the event of significant changes to shot weight (perceived by data from the load cell), the threshold for alarm operation would need to be wide meaning that shot weight could vary significantly within a cycle without operation of the alarm. Furthermore, some known systems, for example as described in US7958915, use dosing rates determined by gravimetric (e.g. load cell) measurements as a basis for speeding up or slowing down a pump thereby to deliver more or less liquid formulation. Figures 6 and 7 illustrate the risks of inaccuracies associated with such a process.

In preferred embodiments, it is considered that the dosing is, first and foremost, volumetric - the calibrated discharge volume of the dosing pump is checked off-line and is then validated during the course of a subsequent run by means of the ultrasonic level-sensor. The loss in weight from the reservoir, as calculated from the analogue level sensor output is compared with the ideal calculated addition rate, as based on the LDR and polymer shot weight or throughput. The user may export this data into a quality system in-order to constantly monitor the difference between the ideal calculated dosing rate and the sensor-measured dosing rate. If the ideal and measured rates differ by more than the user's specified margin, the quality system can raise an alarm which instructs the operator to investigate the cause. By monitoring a sufficiently accurate alarm, the user can reduce or eliminate the need to periodically check the calibration of the metering pump which would normally be required daily. Such checking would require taking the dosing system off-line and stopping the process. By following the embodiment described, unnecessary calibration can be avoided, thereby avoiding material wastage and loss of production time. During periods where the reading from the level sensor is unstable or obscured, the system will continue to dose based on the volumetric calibration and the unreliable readings from the sensors may be excluded from the data-set which will result in a discontinuous data log. The periods during which the reservoir volume is replenished is currently accepted as being unusable data. It would be possible in a more developed embodiment to calculate the delivery rate for certain types of transfer pump and therefore mathematically deduct the contribution of the transfer pump from the overall volume determination and hence overcoming the discontinuous data-set. The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.