JPH0724899A - Resin melting and extruding system - Google Patents

Abstract

PURPOSE:To provide a molten resin extruding system which can construct a resin melting and extruding system with a simple structure and simply conduct a raw material charging and brand switching operation. CONSTITUTION:The resin melting and extruding system comprises a biaxial extruder E, a discharger GP connected in series with a downstream side of the extruder, a plurality of raw material supply units FD for supplying raw material to the extruder, and stable discharge control means LC for calculating molten resin filling amount at an end of the extruder with time on the basis of a discharge pressure, discharging capacity value at the time of operating and physical properties of extrusion molding resin of the extruder and so controlling sending amounts of the units that the calculated filling amounts reach target values. Further, the system comprises raw material transport control means TC for calculating predicted raw material residue in the units at the time of switching the material when a material switching command is input and controlling the material transport amount to the unit according to the result.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin melt extrusion system which comprises a twin-screw extruder and a plurality of weight-controlled quantitative raw material feeders and is capable of mixing and feeding several kinds of raw materials.

[0002]

2. Description of the Related Art Conventionally, when performing melt extrusion of resin, a single screw extruder t is used as shown in FIG. 5, and a raw material is supplied to a hopper of the single screw extruder t. A plurality of silos h1 to h6 for storing the raw materials, and a drying device d1 in the preceding stage for dehumidifying the raw materials sent from the silos
And vacuum-normal displacement hoppers h7 and h8, which are connected to a drying device d2 and a vacuum device v in the latter stage and degass the raw material dehumidified in the previous step, a constant-rate feeder f for controlling the raw material supply amount, and mixing. Machine m and upper hopper h9. In the figure, the line from the vacuum-normal pressure displacement hopper h7 to the single screw extruder t has a vacuum specification.

[0003]

However, in the above-mentioned resin melt extrusion equipment, since a free charge type single-screw extruder t having no drying ability is generally used, a large-scale raw material drying is performed in the preceding step. It is necessary to provide a system, and most of the system needs to have a vacuum specification in order to prevent contamination of water. In addition, when mixing a plurality of raw materials, a mixer m is also required. Therefore,
The conventional free charge type resin melt extrusion equipment using a single-screw extruder has a problem that the initial cost of the equipment is extremely high. Furthermore, since the system from the raw material stock to the single-screw extruder is not only long, but it also has to go through a dryer with an extremely long operating time in that route, the type of raw material and the mixing ratio are changed. At that time, there was a problem that the stocking and switching of the raw materials could not be completed in a short time, and therefore the brand switching operation required a lot of labor and time. The present invention provides a molten resin extruding system capable of constructing a resin melting extruding system with a simple configuration and performing the brand switching operation easily in a short time in consideration of the problems in the conventional resin melting extruding equipment as described above. The purpose is to do.

[0004]

The present invention is directed to a twin-screw extruder, a discharge device connected in series on the downstream side of the twin-screw extruder, and a plurality of raw material feeders for feeding raw materials to the twin-screw extruder. When,
Based on the discharge pressure of the twin-screw extruder, the discharge capacity value during operation, and the physical properties of the resin for extrusion molding, the molten resin filling amount at the tip of the twin-screw extruder was calculated over time, and the calculated molten resin filling amount was Discharge stability control means to control the delivery amount of each raw material feeder to reach the target value, and when the raw material switching instruction is input, calculate the estimated remaining amount of raw material in the raw material feeder at the time of raw material switching, and And a raw material transportation control means for controlling the raw material transportation amount to the raw material supply machine according to the above.

The raw material feeder of the present invention can be composed of a plurality of weight control type hoppers and metering devices for blending a plurality of types of raw materials. In this case, the discharge stability control means has a resin blending ratio. It is preferable that each meter is individually connected so that the amount of material to be delivered can be controlled according to the above. The twin-screw extruder of the present invention preferably has a configuration provided with a plurality of vents, and in this case, the tip portion is a metering zone on the downstream side of the final vent hole. The discharge device of the present invention can include a gear pump, a single-screw extruder, a multi-screw extruder, and the like.

[0006]

In the present invention, when the discharge pressure of the twin-screw extruder is given to the discharge stability control means as the measured or target value, and the extrusion capability value and the resin physical properties of the twin-screw extruder are given, the discharge stability control is performed. The means are based on those data 2
The resin filling amount in the tip portion of the axial extruder is calculated, and the delivery amount of the raw material feeder is controlled so that the calculated resin filling amount becomes a target value. When the raw material switching instruction is input, the raw material transportation control means calculates the expected residual amount of raw material in the raw material feeder when the raw material is switched, and controls the raw material transportation amount to the raw material feeder according to the result. As a result, the discharge amount of the twin-screw extruder in the resin melt extrusion system becomes stable, and the raw material can be easily switched.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a resin melt extrusion system of the present invention. In the figure, FD is a weight control type raw material supply device (raw material supply device), and hoppers H1, H for storing raw material
2 and H3, and belt weighing feeders F1 and F2 and cassette weighing feeders F3 as weighing devices provided for the respective hoppers. In the present embodiment, the belt weighing feeder F
1 is for 15 to 150kg / h, F2 is for 50 to 250kg / h, and cassette weighing feeder F3 is for 50kg / h small amount. These feeders are equipped with a level meter for detecting the upper and lower limits of the raw material and load cells R1 to R3 capable of continuously measuring the rise and fall of the raw material level.

The raw material (hereinafter referred to as resin) supplied from the raw material supply device FD is put into the hopper of the twin-screw extruder E and obtained by rotation of the screw connected to the motor M4 via the reduction gear E1. It receives the thrust force and is pushed out in the pushing direction M. The cylinder of the twin-screw extruder E is connected to a vacuum device V and is provided with a first vent V1 and a second vent V2 for removing volatile components in the resin. Further, in the latter stage (downstream side) of the twin-screw extruder E, pressure increase,
A gear pump GP as a discharge device for improving discharge accuracy is connected in series with the twin-screw extruder E.

Further, a P1 control block PC having a conventional structure for controlling the discharge pressure of the twin-screw extruder E, an L control block LC as a discharge stabilizing control means which is a characteristic part of this embodiment, and a raw material transportation control means. The raw material transport control block TC is composed of a microprocessor. The P1 control block PC is for receiving the discharge pressure value of the twin-screw extruder E detected by the pressure gauge P1 and controlling the motor M4 by an inverter using a conventional predetermined control law.

The L control block L, which is a feature of this embodiment
C is a μ calculation block L1 for calculating a viscosity μ as a resin physical property corresponding to a resin temperature TP detected by a temperature sensor T1, and a screw receiving a coded signal detected by a screw tachometer PG as a pulse generator. Discharge pressure value P, which is connected to the N calculation block L2 for calculating the number of revolutions N, the output of these μ calculation block L1 and the output of the N calculation block L2, and which is detected by the pressure gauge P1.
A constant K determined by the screw shape while receiving 1
L calculation block L3 for executing the L calculation and L
And a supply amount calculation block L5 for executing the calculation of the raw material supply amount using the L control law L4 based on the calculation result of the calculation, and the controllers C1, C2, C3 according to the calculation result.
Controls the motors of the feeders F1 to F3.

A resin temperature-viscosity correspondence table for selecting the resin viscosity μ is stored in advance in a memory (not shown).
, And the constant K is also stored in advance in a memory (not shown). Also, L control law L4
A dead zone L6 is inserted in the preceding stage, and a limiter L7 is inserted between the supply amount calculation block L5 and each of the controllers C1 to C3. The material transport control block TC is connected to the outputs of the load cells R1 to R3, and the hoppers H1 to R3.
By grasping the remaining amount of raw material in H3, the raw material feeding silo (not shown) is controlled.

Discharge Stability Control Before describing the operation of the resin melt extrusion system having such a configuration, the symbols used in the description of the discharge stability control of the twin-screw extruder E are shown below. The discharge stability control is executed for the purpose of keeping the resin filling amount of the tip portion of the twin-screw extruder E at a target value. P1: Discharge pressure Q1: Raw material supply amount Q2: Discharge amount of twin-screw extruder Q3: Discharge amount of gear pump GP N: Screw rotation speed K1: Constant determined by screw shape K2: Constant determined by screw shape μ: Resin physical properties TP : Resin temperature The resin filling amount and other physical amount in L calculation are the following 2
It is related by a formula. ΔL = K1 ∫ΔQdt (1) P1 = K2 μLN (2)

In the equation (1), ΔL represents a resin filling amount change amount (current resin filling amount-previous resin filling amount), and Δ
Q represents a mass balance imbalance amount (raw material supply amount-gear pump discharge amount), and t represents time. By substituting the discharge pressure P1 of the twin-screw extruder into the above formula (2), the present resin filling amount L is obtained, and the filling amount L is obtained from the previously obtained resin amount L.
By comparing with 0, the change amount ΔL of the resin filling length L
Then, the material balance imbalance amount in the raw material supply amount and the discharge amount can be obtained from the differential equation (1).

In this embodiment, the value of P1 substituted into the above equation (1) is an actual measurement value detected from the pressure gauge P1. However, the value of P1 is not limited to this, and may be a target value of P1 control when the conventional P1 control is also used. The reason is that the control cycle (20 msec) for the P1 control is extremely short, and the output is extremely stable due to the inverter control.

Further, FIG. 2 is a cross-sectional view showing the tip side cylinder of the twin-screw extruder E. Inside the cylinder, the pitch of the flight F is arranged differently toward the extruding direction M so that the space where the resin can enter along the screw S can be restricted, and the pitch is narrow near the discharge port. A disposed metering zone Z is provided. This metallic zone Z can be regarded as the "tip portion of the twin-screw extruder" in claim 1. In the figure, the resin filling amount L is the proportion of the resin in the metering zone Z. Actually, the proportion of the resin filled in the direction opposite to the extrusion direction M from the discharge port O is replaced with the length. There is.

Next, the control operation of the resin melting equipment will be described. In FIG. 1, first, the discharge pressure P1 of the twin-screw extruder E detected by the pressure gauge P1, the resin viscosity μ corresponding to the resin temperature TP detected by the temperature sensor T1, and the screw viscosity PG are detected and calculated. The number of revolutions N
Each is given to the L operation block L3.

In the L calculation block L3, the constants K1 and K2 determined by the viscosity μ and the screw shape are read from a memory (not shown), and the resin filling amount at the tip of the twin-screw extruder E is calculated according to the above relational expressions (1) and (2). By calculating L, the amount of change ΔL in the resin filling amount, which is the difference from the previously calculated resin filling amount L0, is calculated by the same process, and the balance imbalance amount ΔQ (raw material supply amount−gear pump discharge amount) is calculated. The calculated balance imbalance amount ΔQ is replaced with a control set value to perform stable discharge control of the twin-screw extruder E. That is, in the control that is processed in the cycle of 200 msec, the resin filling amount L calculated at the present time and the resin filling amount L calculated last time
The difference ΔL with 0 is calculated, and then the balance imbalance amount ΔQ is calculated. If the result is, for example, a value of +, the amount of raw material supplied to the twin-screw extruder E is reduced, and vice versa.
If the value is, the raw material supply amount is increased. At this time, since the raw materials are supplied from the plurality of hoppers H1 to H3 to the twin-screw extruder E, the raw material supply amount is individually controlled according to the raw material mixing ratio in the hopper. The processing operation during steady operation and the material transport control processing operation during brand switching will be described below with reference to the flowcharts.

Steady-state operation process In FIG. 3, first, each weighing feeder F1 to F3.
Is started (step S1), the twin-screw extruder E is checked for abnormality (step S2), and if there is no abnormality, it is determined whether the vent-up sensor is on (step S3).
If the determination result is not on, that is, if vent-up has not occurred, it is further determined whether the raw material supply amount control is set to automatic (step S4). If set to automatic, each weighing feeder F1 to F3
The target value of the discharge amount is calculated (step S5). The target value of the discharge amount is calculated for each of the feeders F1 to F3 in accordance with the raw material supply amount × mixing ratio, and the increase / decrease instruction of the raw material supply amount obtained by the above L control block is given here.

In this way, the system continuously operates under the supervision of the L control block LC, and the above steps S2 to S6 are repeated unless the next brand data is given. If there is an abnormality in the twin-screw extruder E in step S2, an abnormal stop process is performed. If the vent-up sensor is "on" in step S3, the discharge amount of each of the weighing feeders F1 to F3 is immediately reduced by 15% (step S7). Next, it is again determined whether the vent up sensor is "on", and if it is "on", it is determined whether the vent up timer counter has been counted up (step S9). If yes, abnormal stop processing is performed. Move to step S8 to step S2 if no
Return to. Then, when the next brand data is input in step S6, it is determined whether or not it is the brand switching time (step S7), and if "yes", the process moves to the brand (step S11). That is, the data is changed to clear the current setting in memory.

Brand switching process Next, the hold hopper HHO when the brand is changed
The operation of will be described. In FIG. 4, when there is no brand change data (step S20), the L level of the hopper continuously measured is checked (step S20).
21) If the raw material in the hopper is lowered to the L level, the raw material feeding is started (step S22). After the start of the idling, it is checked whether or not the idling congestion is caused (step S23), and if "no", it is checked whether or not the idling is impossible (step S24).
If it is "o", the H level of the hopper is checked (step S25), and if it has risen to the H level, the idling is stopped (step S26). Then, it is checked whether or not the idling can not be stopped (step S27). ), "No", the process returns to step S20.

When the brand change data is input in the above step S20, the required empty delivery amount is calculated (step S
28). For example, assuming that the brand is switched after one hour, the expected remaining amount of the raw material in the hopper at that time is calculated. If the estimated remaining amount is not ≧ 0 (step S29), the hopper level L is confirmed and the supplemental amount is idly fed. If "yes" in step S29, the hopper weight LL is checked (step S30), the hopper level is changed (step S31), and the idling raw material data is changed (step S32). Next, a comparison between the resin melt extrusion system of this example and a conventional resin melt extrusion equipment is shown below.

[0022]

[Table 1]

In Table 1, Comparative 1 is a resin melting facility using a single-screw extruder, and the raw material is supplied by a free charge system. Comparison 2 does not perform the filling amount control of this embodiment 2
The resin melt extrusion equipment using a shaft extruder is shown. As is apparent from the above comparison table, in the present embodiment, the vented twin-screw extruder is capable of stable discharge control, so that it can be incorporated in a resin melt extrusion system for residual amount management and supply amount management. As a result, the raw material can be dried inside the extruder, and the large-scale drying equipment in the former stage of the conventional extruder can be eliminated.

With respect to the mixing ratio of the raw materials, since a plurality of feeders capable of controlling the supply amount are provided, the brands can be switched by simply providing the silo for storing the raw materials before blending for each kind of raw materials. You can do it. Therefore, it is possible to reduce the number of silos required for each type of formulation, as in the conventional configuration. In addition, since a limited number of hoppers can be shared, it is not necessary to take out raw materials, wash, and the like, and the brand switching time can be significantly shortened. Although the discharge stabilization control and the raw material transportation control of the present invention are realized by software using a microcomputer, they may be realized by using a dedicated hardware circuit that performs those functions.

[0025]

As is apparent from the above description, according to the resin melt extrusion system of the present invention, the resin melt extrusion system can be constructed with a simple structure that does not require a large-scale drying facility, Further, it becomes possible to easily carry out the raw material preparation and the brand switching work in a short time.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a resin melt extrusion system according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a tip portion of the twin-screw extruder shown in FIG.

FIG. 3 is a flowchart illustrating an operation of steady operation processing according to the embodiment.

FIG. 4 is a flowchart illustrating an operation of a raw material feeding process according to an embodiment.

FIG. 5 is a configuration diagram showing a molten resin extrusion equipment of a conventional example.

[Explanation of symbols]

 C1 to C3 controller E twin screw extruder FD raw material supply device GP gear pump H1 to H3 hopper LCL control block P1 pressure gauge PC P1 control block TC raw material transportation control block TP resin thermometer

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[Procedure amendment]

[Submission date] June 23, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

In the L calculation block L3, the constants K1 and K2 determined by the viscosity μ and the screw shape are read from a memory (not shown), and the resin filling amount at the tip of the twin-screw extruder E is calculated according to the above relational expressions (1) and (2). By calculating L, the amount of change ΔL in the resin filling amount, which is the difference from the previously calculated resin filling amount L0, is calculated by the same process, and the balance imbalance amount ΔQ (raw material supply amount−gear pump discharge amount) is calculated. The calculated balance imbalance amount ΔQ is replaced with a control set value to perform stable discharge control of the twin-screw extruder E. That is, in the control that is processed in a cycle of 10 seconds , the resin filling amount L calculated at the present time and the resin filling amount L calculated last time
The difference ΔL with 0 is calculated, and then the balance imbalance amount ΔQ is calculated. If the result is, for example, a value of +, the amount of raw material supplied to the twin-screw extruder E is reduced, and vice versa.
If the value is, the raw material supply amount is increased. At this time, since the raw materials are supplied from the plurality of hoppers H1 to H3 to the twin-screw extruder E, the raw material supply amount is individually controlled according to the raw material mixing ratio in the hopper. The processing operation during steady operation and the material transport control processing operation during brand switching will be described below with reference to the flowcharts.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

When the brand change data is input in the above step S20, the required empty delivery amount is calculated (step S
28). For example, assuming that the brand is switched after one hour, the expected remaining amount of the raw material in the hopper at that time is calculated. Expected remaining amount is ≧ 0 if not (step S29), empty send a supplementary amount to check the hopper level L. If "yes" in step S29, the hopper weight LL is checked (step S30), and the hopper weight LL is determined according to the discharge amount.
It is changed to the hopper level (step S31), and the material data for air-feeding is changed (step S32). Next, a comparison between the resin melt extrusion system of this example and a conventional resin melt extrusion equipment is shown below.

Claims (4)

[Claims] 1. A twin-screw extruder, a discharge device connected in series to the downstream side of the twin-screw extruder, a plurality of raw material feeders for feeding raw materials to the twin-screw extruder, and the twin-screw extruder. The molten resin filling amount in the tip portion of the twin-screw extruder is calculated over time based on the discharge pressure of the machine, the discharge capacity value during operation, and the physical properties of the extrusion molding resin, and the calculated molten resin filling amount is the target value. When the discharge stability control means for controlling the delivery amount of each of the raw material feeders and the raw material switching instruction are input,
Resin melting characterized by comprising: a raw material transport control means for calculating an expected residual amount of raw material in the raw material feeder at the time of raw material switching, and controlling the raw material transport amount to the raw material feeder according to the result. Extrusion system. 2. The raw material feeder has a plurality of weight control type hoppers and metering devices for blending a plurality of types of raw materials, and the discharge stability control means is configured to provide the above-mentioned each of the above-mentioned hoppers in accordance with a resin blending ratio. The resin melt extrusion system according to claim 1, wherein the delivery amount of the meter is controlled. 3. The twin-screw extruder comprises a plurality of vents,
The resin melt extrusion system according to claim 1, wherein the tip portion is a metalling zone on the downstream side of the final vent hole. 4. The resin melt extrusion system according to claim 1, wherein the discharge device includes a gear pump, a single-screw extruder, and a multi-screw extruder.