Method for producing thermosetting polymers and low-pressure metering and mixing machine for carrying out said method

Abstract

A method for manufacturing thermosetting polymers and a dispensing machine for implementing said method. The method comprises a metering step, and in particular a calibration of the mass flow of each component, which is fully automatically implemented in order to ensure reliable calibration, without operating or input errors, and to save operator time.

Description

Technical Field

[0001] The present invention relates to a method for the production of thermosetting polymers implemented by a low-pressure metering and mixing machine and preferably to a method for the production comprising an automatic calibration step. Background Art

[0002] Low-pressure dispensing machines for processing polyurethanes or other thermosetting polymers based on formulations having a plurality of reactive components are conventionally also referred to as dispensers, meter-mix or pouring machines and are well known.

[0003] The dispenser comprises a component loop, each loop corresponding to a component of the polymer formulation. Each component loop is usually heated so that the component is liquefied and the component is maintained to be liquid or in the desired viscosity, and each component loop comprises a storage tank for accommodating the component in liquid form. Each component loop can comprise a mixing head, a pump, a first pipe or pipeline leading to a three-way valve arranged at the mixing head, and a second pipe or pipeline returning to the storage tank. Advantageously, each component stream is permanently recirculated, leading to the mixing head and returning to the storage tank to obtain uniform temperature and constant flow rate.

[0004] Typically, when the processing chemistry includes small quantities of reactive chemicals, such as a compact polyurethane formulation (CPU), and when the machine is capable of processing a wide range of formulations at different outputs and back pressures, it is very important to precisely adjust the flow rate of each component to obtain the exact weight ratio and therefore the target stoichiometry.

[0005] When the three-way valve is open, the components flow into the mixing chamber and are mixed via a dynamic mixing turbine, which rotates at high speed and is able to mix the components without introducing air. The liquid reaction mixture is then freely distributed into the mold open cavity or can be injected through a tube connected to the bottom of the closed mold, creating a back pressure of typically less than 10 bar.

[0006] In addition, the pump has internal leakage, which may be more or less serious depending on the quality of the pump, the viscosity of the product being pumped, and the operating pressure and speed of the pump. For a given viscosity, the flow rate is not linear and depends on pressure and speed. In order to obtain accurate and consistent flow of each component, classical technology is widely used, and this classical technology is based on weighing each component manually at a determined (one or more) time to determine the mass flow rate and adjust the pump speed. This technology is called "calibration method" or "external calibration" because the amount of each component is extracted from the machine. The limitation is that when the machine should be in the case of forming various back pressure levels according to the geometric construction and molding method used, with various output distribution multiple groups of ratios of the mixture obtained in the mold or in the container, it will be too long to perform a calibration point for each set of parameters.

[0007] The calibration method is usually manual. The theoretical working pressure for each component is set, and the operator weighs the dispensed product for each component, usually at an average speed or the speed of one component in the recipe, at two different times, and then enters the resulting weight into the machine via the human-machine interface. When the machine dispenses multiple ratios, outputs at different working pressures, the pump deviation is approximately considered constant. The proper setting of the machine depends entirely on the operator, the operator's attention to the weighing operation and the accuracy of the scale. Although improved equipment has been proposed, which uses a scale associated with the machine, the weighing operation is still completed by the operator one component after another.

[0008] Alternative techniques can be used, particularly when no effective pressure control is available, which include equipping each component circuit with a flow meter, either volumetric or mass, in order to avoid frequent calibration and automatically adjust the machine output during pouring. Mass flow meters are often preferred because they are more robust, but this technology is expensive. Summary of the invention

[0009] Based on the above, the object of the present invention is to provide a manufacturing method that can be automatically implemented with accurate precision, in particular because there is no manual operation in the metering step, which is inexpensive.

[0010] For this purpose, the present invention is directed to a process for the manufacture of a thermosetting polymer comprising at least two components, said process comprising at least the following steps:

[0011] - The control unit of the dispensing machine controls the metering of each component,

[0012] - a control unit commands at least one conveying member to convey each component in a mixing chamber of the dispensing machine,

[0013] - the control unit commands the mixing elements of the mixing chamber to mix the metered components,

[0014] - the control unit commands the dispensing device to distribute the obtained mixture in moulds or in containers,

[0015] Wherein the manufacturing method comprises at least one calibration step for each component, comprising:

[0016] a) the control unit commands the mixing head to pour a test amount of the component determined by the initial parameters into a container arranged on a weighing device of the dispensing machine in order to obtain the actual volume of the component,

[0017] b) the weighing device of the dispensing machine weighs the actual volume obtained in step a),

[0018] c) the control unit compares the actual mass of the actual volume weighed in step b) with a theoretical mass determined from the initial parameters used in step a) by using initial relationship data between pump size, pump speed and gravity values ​​determined by default during a determined pouring time,

[0019] d) the control unit determines a correction factor from the comparison in step c), and

[0020] e) the control unit uses the correction factor obtained in step d) to modify the initial relationship data into final relationship data between the output flow rate and the pump speed,

[0021] carrying out said calibration step for at least one measuring point defined by a set of different parameters,

[0022] Wherein the metering step is performed by controlling the pump speed to obtain a desired mass flow of the components, the control unit controls the pump speed by using the final relationship data obtained in step e).

[0023] Thanks to this manufacturing method and dispensing machine of the invention, the metering step and in particular the calibration of the mass flow is fully automatically implemented. Furthermore, the dispensing machine of the invention guarantees a reliable calibration, without operating or input errors, and saves the operator's time.

[0024] According to a feature of the invention, the initial parameter can be the pump speed and / or the pump operating pressure.

[0025] According to a feature of the invention, the calibration step can be carried out for several measuring points, preferably for three to eight measuring points, which are regularly or irregularly distributed with respect to the pump speed range and / or the pump operating pressure. Advantageously, for each measuring point, a correction factor associated with the selected pump speed is determined by step d) and recorded in the control unit by recording means, such as a memory integrated in the control unit.

[0026] According to a feature of the invention, each measuring point is configured to cover the entire pump speed range and pressure range in an optimized manner.

[0027] According to a feature of the invention, steps a) to e) are performed continuously.

[0028] According to a feature of the invention, due to the use of a dynamic pressure regulator on each inlet, the pressure is no longer the initial parameter, the measuring points are only at different pump speeds. Therefore, the measuring points are only implemented for various pump speeds, since the pump operating pressure is preferably controlled via a dynamic pressure regulator, which is able to maintain a constant pressure level independently of the pressure generated by the process downstream of the mixing head.

[0029] According to a feature of the invention, the control unit comprises a memory configured to record the history of the calibration steps. This feature allows quality assurance, production troubleshooting and maintenance analysis. Advantageously, the manufacturing method comprises a step g) in which the memory of the control unit records the history of the final relationship data for each measurement point of each component.

[0030] According to a feature of the invention, the manufacturing method comprises a step h) in which the control unit uses a record of the history of the final relationship data; and a step i) in which the control unit suggests instructions for calibration adjustment and / or pressure adjustment based on the record used in step h). This feature allows helping the operator to follow a strict process and provides an accurate and reliable process.

[0031] According to a feature of the invention, the calibration adjustment can be an evaluation of the frequency of implementation of the calibration step. For example, for a determined period of time, if the calibration step has not been implemented, the control unit proposes to implement said calibration step in order to work with accurate parameters. Advantageously, the operator can set the frequency of implementation of the calibration step.

[0032] According to a characteristic of the invention, the dispensing machine and the control unit are destined to dispense multiple recipes, multiple outputs, with different back pressures generated by the mould.

[0033] Another object of the present invention is to provide a dispensing machine, such as a low-pressure metering and mixing machine, configured to manufacture a thermosetting polymer based on at least two different components, the dispensing machine comprising at least:

[0034] - control unit,

[0035] - Human Machine Interface connected to the control unit,

[0036] a mixing head equipped with at least two inlets for at least two components and an outlet and a return for each of the at least two components,

[0037] - a pump configured to control the flow of the components,

[0038] - a mixing chamber equipped with mixing elements, the mixing chamber being configured to mix the components together,

[0039] - a distribution device configured to distribute the mixture obtained in the mixing chamber,

[0040] Characterized in that the dispenser comprises an integrated weighing device, which is configured to be movable from at least an inactive position, in which the weighing device is arranged in the dispenser device, to at least one active position, in which the weighing device protrudes from the dispenser device by translation and / or rotation, in which the weighing device is positioned below the mixing head and is connected to a control unit, wherein the control unit is configured to control the weighing device.

[0041] Thanks to the dispensing machine with integrated weighing device, accurate and reliable weighing values ​​can be collected, since the weighing device is directly connected to the control unit which collects the weighing values ​​regarding the mass of the weighed volume of the component without the need for an operator.

[0042] According to a characteristic of the invention, the dispensing machine of the invention allows the manufacturing method of the invention to be implemented.

[0043] According to a characteristic of the invention, the dispensing machine comprises a dynamic pressure regulator. The calibration process combined with the dynamic pressure control allows to eliminate the influence of the pressure generated by the molding on the pump, so that the pump can be calibrated according to the speed in order to dispense multiple recipes, various outputs and pouring methods with excellent precision. Thanks to the dynamic pressure regulator, only the pump speed remains in the parameter set.

[0044] According to a feature of the invention, the dynamic pressure regulator of the dispenser machine is able to maintain a constant pressure level independently of the pressure generated by the process downstream of the mixing head.

[0045] According to a feature of the invention, a dynamic pressure regulator is configured to restrict material flow with a moving piston or biasing member having an adjustable force, so that any increase in downstream pressure will increase the restriction area, so that the upstream total pressure will remain approximately constant. The dynamic pressure regulator allows the operator to add additional operating pressure greater than the operating pressure that the operator may require during various casting operations, and so that any additional downstream back pressure will cause the regulator to self-adjust to maintain a constant upstream operating pressure for the pump. The pressure can then be set to a defined sufficient level for each component, and then a careful external calibration and corresponding output adjustment can be performed. Then, regardless of the casting method and back pressure, during the working period, the machine will accurately deliver a constant output of each component, keeping the ratio unchanged.

[0046] According to a feature of the invention, the weighing device comprises an arm supporting the load cell at one end.

[0047] According to a feature of the invention, when a container is positioned on the load cell, the presence of said container is detected and the control unit receives such information to start a calibration step. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The invention will be better understood thanks to the following detailed description, which describes an embodiment of the invention by way of example and based on the following drawings.

[0049] Figure 1 is a graphical representation of the initial relationship data, the final relationship data, and the relationship data without correction factors between the output flow rate and the pump speed.

[0050] Figure 2 is a side view of a dispensing machine according to the present invention,

[0051] Figure 3 is a perspective view of a dispensing machine according to the invention. DETAILED DESCRIPTION

[0052] exist Figure 2 and 3 The dispensing machine 100 of the present invention illustrated in FIG is a low-pressure metering and mixing machine. The dispensing machine 100 is configured to manufacture thermosetting polymers based on at least two different components by implementing the manufacturing method detailed below.

[0053] According to the present invention and as Figure 2 and Figure 3 , the dispensing machine 100 comprises a control unit 101, a human-machine interface 102 connected to the control unit 101. The dispensing machine 100 comprises a mixing head 103, which is equipped with at least two inlets 103a for at least two components and a circuit 103b for each of the at least two components. The components are stored in a container 107. The dispensing machine 100 also comprises: a pump 104, which is configured to control the flow of the components reaching the mixing head 103; a mixing chamber 105 equipped with a mixing element (not shown), which is configured to mix the components together; and a dispensing device (not shown), which is configured to distribute the mixture obtained in the mixing chamber 105 into a mold or a container (not shown).

[0054] According to the present invention, the dispensing machine 100 comprises a slidably integrated weighing device 106. The weighing device 106 comprises an arm 106a at one end of which a weighing sensor 106b is arranged. The weighing device 106 is configured to be movable from at least one inactive position (in Figure 2106 is moved to at least one active position, in which the weighing device 106 is arranged in the dispensing machine 100, and in which the weighing device 106 protrudes from the dispensing machine 100 by translation and / or rotation. Figure 2 and 3 As shown in FIG. 1 , the weighing device 106 is positioned below the mixing head 103 in an active position.

[0055] The control unit 101 is configured to control all elements of the dispensing machine 100 , such as the mixing head 103 and the inlet of the mixing head 103 preferably equipped with a dynamic pressure regulator 103 a , the pump 104 , the weighing device 106 , the mixing chamber 105 , the human-machine interface 102 .

[0056] In order to manufacture thermosetting polymers, the dispensing machine 100 implements the manufacturing method to be described above. First, the operator needs to select or input the component to be calibrated. This selection or this input can be implemented in the control unit 101 via the human-machine interface 102. Then, if the inlet 103a is preferably equipped with a dynamic pressure regulator, the operator can adjust the working pressure to be above the back pressure required for the pouring process.

[0057] Then, the control unit 101 carries out a calibration step for each component. To this end, the control unit commands the weighing device 106 to move into the active position, or the operator moves the weighing device 106 into the active position. Once the weighing device 106 is in the active position, the control unit 101 commands the mixing head 103 to pour the test amount of the component determined by the initial parameters into the container 1 arranged on the weighing device 106 of the dispensing machine 100, so as to obtain the actual volume of the component, as in Figure 2 and 3 This command is executed only when a container 1 is detected on the weighing device 106. When a container 1 is positioned on the weighing sensor 106b, the presence of said container 1 is detected and the control unit 101 receives such information to start the calibration step.

[0058] A test amount of a component is poured in and the actual volume of the test amount of the component is weighed by the weighing device 106. The weighing device 106 sends the weight information to the control unit 101.

[0059] The control unit 101 compares the actual mass of the actual volume with the theoretical mass determined by the initial parameters using the initial relationship data between the output flow rate and the pump speed. The initial relationship data is graphically represented in FIG. Figure 1, while the actual mass is shown in triangles. For simplification purposes, in order to better show the nonlinear deviations, the deviations are shown as multiplication factors and the gravity value determined is 1. The deviations are represented by crosses and illustrate the difference between the actual output and the theoretical output.

[0060] The control unit 101 then determines a correction factor for the calibration at the determined pump speed, which in the graph is at 30% of the full pump speed, corresponding to a deviation of 2% on the graph.

[0061] Since the deviation is not constant and may vary with the pump speed, for better results, the calibration step is carried out for several measuring points defined by a set of different pump speeds. In a preferred embodiment, if the pressure of each component is stable due to the dynamic pressure regulator, it is not necessary to perform calibration points at different pressures. The pump speed parameter alone is sufficient to obtain all necessary correction factors. For each zone of the pump speed range, the control unit will be able to meter the components taking into account the appropriate correction factors to deliver the amount and mass flow rate of the product according to the recipe of the components.

[0062] When all measuring points of a component are calibrated, the control unit can, at the operator's option, carry out the same calibration procedure for the other component(s).

[0063] The control unit then commands at least one conveying member to convey each component in the mixing chamber 105 of the dispenser 100 and commands the mixing elements of the mixing chamber 105 to mix the metered components. Finally, the obtained mixture is dispensed or injected in a mold or in a container.

[0064] The invention is applicable to any low pressure metering and mixing machine. In the example of a three or four component machine, if the machine is equipped with a dynamic pressure regulator, the machine is capable of processing a wide range of formulations at different outputs and with different back pressures generated by the mold. The invention provides a novel, simple (only 3 to 8 measurement points) and automatic way of calibration, which has superior accuracy compared to traditional methods.

[0065] Obviously, the invention is not limited to the embodiments described and represented by the drawings. Modifications are still possible without leaving the entire scope of the invention, particularly from the point of view of the composition of each element or by substitution of technical equivalents.

Claims

1. A method for producing a thermosetting polymer comprising at least two components, the method comprising at least the following steps: - The control unit of the dispensing machine controls the metering of each component, - the control unit commands at least one conveying member to convey each component in the mixing chamber of the dispenser, - the control unit commands the mixing elements of the mixing chamber to mix the metered components, - the control unit commands the dispensing device to distribute the obtained mixture in molds or in containers, Wherein, the manufacturing method comprises at least one calibration step for each component, comprising: a) the control unit commands the mixing head to pour a test amount of a component determined by the initial parameters into a container arranged on a weighing device of the dispensing machine in order to obtain the actual volume of the component, b) the weighing device of the dispensing machine weighs the actual volume obtained in step a), c) the control unit compares the actual mass of the actual volume weighed in step b) with a theoretical mass, wherein the theoretical mass is determined from the initial parameters used in step a) by using initial relationship data between pump size, pump speed and gravity values ​​determined by default during a determined pouring time, d) the control unit determines a correction factor from the comparison in step c), and e) the control unit modifies the initial relationship data into final relationship data between output flow rate and pump speed using the correction factor obtained in step d), carrying out said calibration step for several measurement points defined by a set of different parameters, Wherein the metering step is performed by controlling a pump speed to obtain a desired mass flow of the component, the control unit controls the pump speed by using the final relationship data obtained in step e).

2. The manufacturing method according to claim 1, wherein: The initial parameters can be the pump speed and / or the pour time and / or the pump pressure.

3. The manufacturing method according to claim 1 or 2, wherein: The steps a) to e) are performed continuously.

4. The manufacturing method according to claim 1 or 2, wherein: Due to the use of dynamic pressure regulators at each inlet, the pressure is no longer the primary parameter, the measuring points are only at different pump speeds.

5. The manufacturing method according to claim 1 or 2, comprising step g), wherein: The control unit includes a memory that records a history of final relationship data for each component.

6. The manufacturing method according to claim 5, comprising step h), wherein: The control unit uses a record of the history of the final relationship data to identify components that have been calibrated; and step i), wherein the control unit suggests instructions for calibration adjustment and / or pressure adjustment based on the record used in step h).

7. The manufacturing method according to claim 1 or 2, wherein: The dispensing machine and the control unit are destined to dispense multiple recipes, multiple outputs, at different back pressures generated by the mold.

8. A dispensing machine configured to implement the manufacturing method according to any one of claims 1 to 7 and configured to manufacture a thermosetting polymer based on at least two different components, the dispensing machine comprising at least: - control unit, - a human-machine interface connected to the control unit, a mixing head equipped with at least two inlets for the at least two components and an outlet and a return for each of the at least two components, - a pump configured to control the flow of said components, - a mixing chamber equipped with mixing elements, said mixing chamber being configured to mix said components together, - a distribution device configured to distribute the mixture obtained in the mixing chamber, Characterized in that the dispensing machine comprises an integrated weighing device, which is configured to be movable from at least one inactive position, in which the weighing device is arranged in the dispensing device, to at least one active position, in which the weighing device protrudes from the dispensing device by translation and / or rotation, in which the weighing device is positioned below the mixing head and is connected to the control unit, wherein the control unit is configured to control the weighing device.

9. Dispensing machine according to claim 8, comprising a dynamic pressure regulator.

10. The dispensing machine according to claim 9, wherein: In use the dynamic pressure regulator is able to maintain a constant pressure level independent of the pressure generated by the mixing process downstream of the mixing head.

11. The dispensing machine according to claim 8, wherein: The dispensing machine is a low pressure metering and mixing machine.

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