JPH1058444A - Method and apparatus for controlling continuous kneader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a kneaded substance with an optimum quality by controlling operating condition of a continuous kneader in such a way that actually measured temp. and specific energy of a resin are made to set values. SOLUTION: An enthalpy curve and the converging value (permissible error) being inherent in a material as well as specific energy or resin temp. of a kneaded resin material to be obtd. are set and are inputted into a storage means. After initiation is set, operation of a kneader 2 is started and the amt. of a material fed into the kneader 2 from a raw material feeding device 1 is measured by a production amount measuring means 15 and the electric energy consumption of a kneader driving motor 6 is measured by the first electric energy measuring means 16 and at the same time, the resin temp. at the outlet of the kneader 2 is measured by the first temp. measuring means 18. From the amt. of production and the electric energy measured by the actually measuring means 11, specific energy is obtd. by an operating means 12 and when there exists a difference being out of a permissible range between a set specific energy and the actually measured specific energy by a comparison means 13, it is adjusted within the permissible range by a controlling means 14 and when it is within the permissible range, stable operation is performed. It is possible to perform highly accurately controlling and to obtain improvement and stabilization of the quality and a uniform kneaded substance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method and a control apparatus for a continuous kneader used for producing pellets for forming plastic products such as films, sheets, pipes, containers and the like.

[0002]

2. Description of the Related Art In a continuous kneader, a polymer material is continuously supplied to a kneading chamber by a raw material supply device, and a kneading rotor arranged in the kneading chamber is rotated by an electric motor to knead the supplied material. While extruding along the rotor to form a pellet product.

[0003] The quality of the pellet product depends on the kneading in the kneading machine.
The control of operating conditions is extremely important, as it leads to poor quality. As a control of a conventional continuous kneader, for example, there is one described in JP-A-4-125123.

In this conventional apparatus, the inlet pressure of a gear pump disposed between a kneader and a molding machine is measured, and the operation of the kneader is controlled by comparing the measured value with a set value. . However, in this method, the selection of the setting value must be determined by human experience, and requires trial and error. Further, the setting value itself has no physical meaning. Therefore, when the material is changed, the setting has to be performed while repeating trial and error. Even though the driving operation is online, it cannot be said that the quality is directly controlled.

That is, in this conventional apparatus, trial and error must be performed in order to obtain an optimum kneaded material, which is wasteful, and it is impossible to directly control the quality of the kneaded material. Further, the prior art described in JP-A-5-131521 is to take out a sample resin from an extruder, measure the state of the sample resin, and feed it back to operating conditions.

However, this method requires a gear pump for collecting the sample resin, which not only increases the cost of the apparatus, but also wastes the material. In addition, the resin is extruded by the newly installed gear pump. May change its physical properties. On the other hand, JP-A-4-2267
The conventional device described in Japanese Patent Application Publication No. 08-0808 uses the power consumption (specific energy) per unit production for quality control.

However, a kneaded material of good quality could not be obtained by controlling only the specific energy. It is impossible to stably produce high-quality kneaded materials unless factors directly related to quality are incorporated into the control at the same time as specific energy. However, these factors are not disclosed or suggested in this prior art. It has not been.

[0008]

SUMMARY OF THE INVENTION The present invention is not to control the operating conditions by detecting the pressure before the conventional gear pump, collecting the sample, or setting only the necessary specific energy. Another object of the present invention is to obtain a kneaded material having an optimum kneading quality by using specific energy and other factors which are directly related to the kneading quality.

[0009]

In order to achieve the above object, the present invention takes the following measures. That is, the feature of the control method of the present invention is that the operating conditions of the continuous kneader are controlled so that the resin temperature and the specific energy measured in the continuous kneader become set values.

The resin has specific data called enthalpy curve as a characteristic specific to the material. This enthalpy curve is data directly related to the physical properties of the resin. The horizontal axis indicates the resin temperature (° C), and the vertical axis indicates the specific energy (kw · h).
/ Kg), it is uniquely the same as the enthalpy curve if the relationship drawn when taking is obtained. Note that the specific energy refers to the amount of power consumption (kw) per unit production (kg / h).

Since the enthalpy curve is a characteristic inherent to the material, it can be said that the material is in the best condition if the material in the kneaded state matches this characteristic in the continuous kneader. . That is, in the present invention, the resin temperature and the specific energy are actually measured, and the operating conditions are controlled so that the measured value becomes a preset value specific to the material.
The kneaded material is maintained at the best quality.

More specifically, a resin temperature and a specific energy corresponding to the kneading material are set, and after starting the operation, a production amount, an electric energy, and a resin temperature are measured, and the specific energy is determined from the production amount and the electric energy. And the set resin temperature and specific energy are compared with the actually measured resin temperature and specific energy, and when the difference between the two is outside the allowable range, the operating conditions are automatically controlled so as to be within the allowable range.

The continuous kneading machine includes a kneading rotor whose rotation speed is adjustable and a gate whose opening is adjustable. The operating conditions to be automatically controlled are a rotor rotation speed and a gate opening. Either one may be used, and the present invention is not limited to this. The setting of the resin temperature and the specific energy is preferably performed in a function form, but may be performed in a table form.

When a gear pump whose rotation speed is adjustable is installed downstream of the kneader, the gear pump rotation speed is added to the operating conditions to be automatically controlled. As a control device of the continuous kneader of the present invention, a storage means for storing a set value of the resin temperature and specific energy corresponding to the kneaded material, an actual measurement means for measuring the production amount, the electric energy and the resin temperature, Computing means for calculating the specific energy from the production amount and the electric energy by the actual measuring means, and comparing the set resin temperature and specific energy with the actually measured resin temperature and specific energy, and when the difference between the two is outside the allowable range. And control means for automatically controlling the operating conditions so as to fall within the allowable range.

The continuous kneader includes a kneading rotor whose rotation speed is adjustable and a gate whose opening is adjustable.
The apparatus includes means for measuring the amount of raw material supplied, means for measuring the amount of electric power, and means for measuring the temperature of the resin at the outlet of the kneading machine. Degrees.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram relating to a control device of a continuous kneader. This apparatus comprises a raw material supply device 1 for continuously supplying materials,
Kneader 2 for kneading and melting the material supplied from the mixer, a gear pump 3 for feeding a predetermined amount of the molten resin from the kneader 2, and a molding machine 4 for granulating the resin supplied from the gear pump 3 into pellets. And

The raw material supply device 1 is constituted by, for example, a screw extruder or the like, and is capable of controlling the amount of material supplied to the kneader 2. The kneading machine 2 is provided with a kneading rotor 5 for kneading and melting the material, a motor 6 capable of adjusting the speed of rotation of the rotor 5 and a gate device 7 for adjusting a passage area of the molten resin. ing. The gear pump 3 is driven by a motor 8 whose speed can be adjusted.

The operation of the raw material supply device 1, kneader 2 and gear pump 3 is automatically controlled by a control device 9. The control device 9 includes a storage unit 10 that stores a set value of a resin temperature and a specific energy corresponding to the kneaded material, an actual measurement unit 11 that measures a production amount, an electric energy, and a resin temperature,
A calculating means 12 for obtaining a specific energy from a production amount and an electric energy by the actual measuring means 11; a comparing means 13 for comparing the set resin temperature and specific energy with the actually measured resin temperature and specific energy; And control means 14 for automatically controlling the operating conditions so that the operating condition is within the allowable range when the value is outside the allowable range.

The storage means 10 stores the enthalpy curve shown in FIG. This enthalpy curve is data that the material has as its unique characteristics, and can be obtained in advance as a relationship between specific energy and resin temperature. The enthalpy curve is held by the material manufacturer as data and is publicly available. “HDPE” in FIG. 2 means “High Density Poly Ethylene”. The storage format in the storage means 10 is, for example, the relationship shown in FIG. 2 linearly interpolated and stored as a continuous function of three linear functions a, b, and c, but is not limited to this.

The actual measuring means 11 is a production amount measuring means 15 for measuring the amount (kg / h) of the material supplied from the raw material supply device 1 to the kneading machine 2, and the power consumption (kwh) of the motor 6 of the kneading machine 2. ), The second power amount measuring means 17 for measuring the power consumption of the motor of the gear pump 3, the first temperature measurement for measuring the resin temperature (° C.) at the kneader outlet. The means 18 and the second temperature measuring means 19 for measuring the resin temperature at the outlet of the gear pump 3 are exemplified.

The production amount measuring means 15 calculates the feed amount by detecting the number of rotations of the feed screw, or
It consists of a flow meter or the like that measures the actual supply amount. As the electric power measuring means 16 and 17, an integrator or the like for obtaining an electric energy from a current value and a voltage value is used. The operating conditions to be controlled by the control means 14 are the rotor speed of the kneader 2 and the gate opening, but other factors such as the gear pump speed and the pressure before the gear pump are controlled. Is also good. In a system without a gear pump, it is also possible to control the rotor speed, gate opening, and outlet pressure.

A control method in the case where the apparatus does not have a gear pump will be described with reference to the flow chart shown in FIG.
First, the enthalpy curve (see FIG. 2) specific to the material is stored in the storage means 10. Since the enthalpy curve is material-specific data, it is stored in advance for each type of material, and in actual production, when the type of raw material is determined,
Make sure that the data can be called from the database. At the same time, the convergence value (allowable error) is stored.

Next, the specific energy or the resin temperature of the kneaded resin material to be obtained, which is empirically grasped, is set and input (if one is determined, the other is uniquely determined). The materials are kneaded to set this initial value. After completion of the initial setting, the operation of the kneading machine 2 is started. After the start of the operation, the amount of material supplied from the raw material supply device 1 to the kneading machine 2 is measured by the production amount measuring means 15 and the first amount is measured.
The amount of power consumption of the kneader drive motor 6 is measured by the power amount measuring means 16. At the same time, the resin temperature at the outlet of the kneader 2 is measured by the first temperature measuring means 18.

The specific energy is obtained by the calculating means 12 from the production amount and the electric energy by the actual measuring means 11. The comparing means 13 compares the set specific energy at the actually measured resin temperature with the actually measured specific energy. When the difference between the two is outside the allowable range (convergence value), the control means 14 sets the specific energy within the allowable range. The rotor speed and the gate opening are adjusted so as to be as possible.

Thereafter, the same is repeated, and if the difference between the set specific energy and the measured specific energy falls within an allowable range, stable operation is started, and the operating conditions of the controlled object are fixed.
The monitoring mode is set at a certain interval. The above is the control flow in the kneader 2, but the case where the gear pump 3 is installed downstream of the kneader 2 will be described below.

The resin coming out of the outlet of the kneader 2 flows by the pressure generated by the gear pump 3 and generates heat in the flow path. Therefore, the control value obtained by controlling based on the condition on the exit side of the kneader 2 does not follow the enthalpy curve. Therefore, a control for adjusting the gear pump rotation speed is added so that the gear pump outlet temperature is measured by the second temperature measuring means 19 and the enthalpy corresponding to this temperature is obtained. Then, similarly to the control when only the kneading machine 2 is used, the same operation is repeated until the allowable value is reached, and then the stable operation is started.

[0027]

4 and 5 show a comparison between an embodiment of the present invention and a conventional example. FIG. 5 is an enlarged view of FIG. In the same figure, the embodiment of the present invention is indicated by a black circle, the conventional example is indicated by a white circle, and shows two results of control at the kneader outlet and control at the gear pump outlet.

When the control was performed by the method of the present invention, the temperature variation was conventionally ± 20 ° C., but was now within ± 10 ° C. And as a result of actual sample evaluation,
A kneaded product having a small temperature variation and a uniform molecular weight distribution and a uniform melt viscosity was obtained. It should be noted that the present invention is not limited to the above-described embodiment and examples.

[0029]

According to the present invention, since the operating conditions are controlled by the enthalpy curve which is directly related to the physical properties, it is possible to perform a highly precise control which has not been achieved conventionally. In addition, since it is also possible to separately control the kneading unit and the extruding unit in each unit based on data specific to each resin called enthalpy curve, the configuration of the kneading granulator, for example, depends on the presence or absence of a gear pump. Without this, it is possible to control the kneading quality.

Since enthalpy curves each having a unique physical meaning are set and input for various materials, there is no problem even if the type of resin is changed. Make changes fast.
It is possible to eliminate an excessive energy input that causes resin deterioration, to improve and stabilize the quality, and to obtain a uniform kneaded material.

If the measured value is above the set enthalpy curve, it means that there is a high possibility that the unmelted resin is present, and it is possible to perform control to eliminate the unmelted resin. It is also possible to detect the presence of unmelted resin.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a control device of a continuous kneader.

FIG. 2 is a graph showing an enthalpy curve of HDPE.

FIG. 3 is a flowchart of a control method according to the present invention.

FIG. 4 is a graph showing a comparison of effects between the method of the present invention and a conventional example.

FIG. 5 is an enlarged view of FIG. 4;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 raw material supply device 2 kneader 3 gear pump 5 kneading rotor 6 motor (for kneader) 7 gate device 8 motor (for gear pump) 9 control device 10 storage unit 11 actual measurement unit 12 calculation unit 13 comparison unit 14 control unit 15 production amount measurement Means 16 First electric energy measuring means 17 Second electric energy measuring means 18 First temperature measuring means 19 Second temperature measuring means

Continued on the front page (72) Inventor Masahiko Kashiwa 2-3-1, Shinhama, Arai-machi, Takasago City, Hyogo Prefecture Inside Kobe Steel, Ltd. Takasago Works (72) Inventor Shigehiro Kasai 2-3-1, Shinama, Arai-machi, Takasago City, Hyogo Prefecture No.In Kobe Steel, Ltd.Takasago Works

Claims (7)

[Claims] 1. A method for controlling a continuous kneader, wherein operating conditions of the continuous kneader are controlled such that a resin temperature and a specific energy measured in the continuous kneader become set values. 2. A resin temperature and a specific energy corresponding to the kneading material are set, and after starting the operation, a production amount, an electric energy, and a resin temperature are measured, and the specific energy is obtained from the production amount and the electric energy. The set resin temperature and specific energy are compared with the actually measured resin temperature and specific energy, and when the difference between the two is outside the allowable range, the operating condition is automatically controlled to be within the allowable range. Control method of continuous kneader. 3. The continuous kneader includes a kneading rotor whose rotation speed is adjustable and a gate whose opening is adjustable, and the operating conditions to be automatically controlled are a rotor rotation speed and a gate opening. The method for controlling a continuous kneader according to claim 2, wherein 4. The control method for a continuous kneader according to claim 2, wherein the setting of the resin temperature and the specific energy is performed in a function form. 5. The method according to claim 3, wherein when a gear pump whose rotation speed is adjustable is installed downstream of the kneader, the rotation speed of the gear pump is added to the operating conditions to be automatically controlled. Control method of continuous kneader. 6. A storage unit for storing a set value of a resin temperature and a specific energy corresponding to a kneading material, an actual measuring unit for measuring a production amount, an electric energy, and a resin temperature, and a production amount and an electric power by the actual measuring unit. Calculating means for calculating the specific energy from the amount, comparing the set resin temperature and specific energy with the actually measured resin temperature and specific energy, and when the difference between the two is outside the allowable range, the difference falls within the allowable range. A control device for a continuous kneader, comprising: control means for automatically controlling operating conditions. 7. A continuous kneader includes a kneading rotor capable of adjusting the number of revolutions and a gate capable of adjusting an opening. The actual measuring means includes means for measuring a raw material supply amount, a means for measuring a power amount, and kneading. 7. The control of the continuous kneading machine according to claim 6, further comprising means for measuring a resin temperature at an outlet of the kneading machine, wherein operating conditions controlled by the control means are a rotor speed and a gate opening. apparatus.