JPH11254499A - Method for switching molding material of extrusion molding and apparatus for supplying molding material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for switching a molding material without trouble such as a retention, a thermal decomposition or the like in a mold without necessity of an expensive stop material in the case of switching the material on the way of the molding and an apparatus for supplying the material. SOLUTION: The method for switching a molding material comprises the steps of inputting a rotational speed r of a screw feeder 8 of an extruder 1, an inner volume V1 of a barrel, an inner volume V2 of a mold 10, detected values of level detectors 91, 92 of a main hopper 2 and the like to a calculator 11, calculating a timing of starting and stopping rotary valves 51, 52, discharging the later material in a sub-hopper 31 to a main hopper 2 while discharging the previous material in the hopper 32 by using the apparatus for supplying the material, for automatically operating, mixing them by an agitator 6, supplying it to the extruder 1, then stopping the supply of the previous material, and supplying only the later material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for switching a molding material in extrusion molding and an apparatus for supplying the molding material, and particularly to a chlorinated vinyl chloride resin (hereinafter referred to as "C-PVC").
And a method for safely switching the compounding of raw materials without damaging an extrusion mold (hereinafter referred to as a "mold") while continuously extruding a molding material mainly composed of The present invention relates to a molding material supply device.

[0002]

2. Description of the Related Art C-PVC is an ordinary vinyl chloride resin (P
VC) is a resin that has been further chlorinated and has a thermal stability of P
It is worse than VC, and has a disadvantage that when exposed to a high temperature, the dehydrochlorination reaction proceeds in a relatively short time, generating chlorine gas which is toxic and has the property of corroding metals. Also, C-PV
C is inferior to PVC in fluidity in a molten state, so that it has poor slip at the contact surface between the molten resin and the mold, and has poor moldability, so that it is difficult to produce at a high throughput.

[0003] Despite having the above-mentioned problems, a tube (C-PVC tube) extruded with a raw material mixture containing C-PVC as a main material is called a heat-resistant vinyl tube,
General rigid vinyl chloride tube (U-PVC tube) such as 5 ° C
It has the feature that it can be used even at high temperatures where it cannot be used, and is widely used. In such applications, molding materials having a compounding composition in which a large amount of a lubricant is added are mainly used for the purpose of improving flowability in a molten state and improving moldability.

However, when the C-PVC pipe is used as a transport pipe for hot chlorine water or caustic soda, the lubricant contained in the molding material undergoes a decomposition reaction due to a strongly acidic or strongly alkaline substance and elutes. There is a problem that the mechanical strength of the tube is reduced. Therefore, for example, in a C-PVC pipe not used for transporting high-temperature chlorine water or caustic soda, for example, for hot water supply, a molding material having a compounding composition with a reduced amount of a lubricant is mainly used.

[0005] As described above, a molding material having a compounded composition with a large amount of lubricant added (referred to as A compound) and a molding material with a compounded composition having a small amount of lubricant added (referred to as B compound) are used depending on purposes. It is used properly. Table 1 shows the composition of each molding material.

[0006]

[Table 1]

By the way, in extruding, when the extruder is stopped in order to stop the production, in order to avoid an accident accompanying the thermal decomposition of the molding material during the stop work or the mold disassembly, the molding material currently used is not used. It is usual to switch from to a molding material for stopping (referred to as “stop raw material”). Further, in order to continue using the same mold to produce products having different composition, the extruder may be operated to switch from the molding material being extruded to a molding material having another composition. In such a case, by switching the molding material, the drift or the thermal decomposition occurs as described above, which causes danger to the human body, damages equipment such as an extruder and a mold, or generates a large amount of raw material loss. Care must be taken to avoid any significant downtime and a significant drop in productivity.

In particular, when a molding material having low thermal stability and poor fluidity, such as the B compound in Table 1 above, is left in a mold for a long time, the dehydrochlorination reaction of the C-PVC resin proceeds, Toxic chlorine gas is generated in the human body, and as a result, the plating of the mold and the surface of the steel material as the structural material may be damaged.

Therefore, as an actual example, a description will be given of a method (procedure) for extruding the above-mentioned B compound, a case of discontinuing the production which has been conventionally performed, and a method of switching from the B compound to the A compound. (1) When the production is stopped (when the extruder is stopped) A stop raw material having excellent heat stability and very good fluidity is prepared separately. The supply of the B compound to the extruder is stopped, and subsequently, the extruder is switched to the stop raw material, and the extruder is stopped when the stop raw material is filled in the mold. The mold is removed from the extruder and dismantled to remove the internal stop material. The extruder is stopped while the mold is filled with the B compound. The mold is removed from the extruder and dismantled to remove the B compound inside. (2) When extruding is continued after switching from B blend to A blend, supply of the B blend to the extruder is stopped, and then the A blend is supplied, and the B blend in the mold is replaced with the A blend and switched. 3
It is on the street.

Of these methods, the method of
In order to simply switch to the blending, it is necessary to prepare a stop raw material in which the amount of the heat stabilizer and the lubricant is increased, and there is a problem that extra material cost and man-hour cost are required. In the method (1), if the mold is not dismantled quickly, the dehydrochlorination reaction of the resin in the mold proceeds due to heat, and thermal decomposition is likely to occur.
Therefore, there is a problem that it is difficult to carry out the method for a large-sized mold requiring a long time for dismantling or a mold having a complicated structure. In addition, the method of (1) has a large difference in fluidity due to a large difference in the amount of the lubricant added between the A and B formulations. In a place where it is easy to perform, for example, in a spider portion of a tube extrusion molding die or an enlarged portion in front of the spider portion, only a flowable A compound with a large amount of lubricant is passed, and a compound B with a small amount of lubricant is difficult to flow. The so-called drift occurs due to stagnation, and it may take a long time to obtain a product, or the product may not be obtained. In addition, as a result of the B mixing remaining in the mold for a long time due to the drift, thermal decomposition may occur.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and is intended to stop production in extrusion molding or to continue production using the same mold. In the case of switching the molding material in order to do so, there is no need to prepare expensive stop raw materials, and there is less occurrence of thermal decomposition due to stagnation, loss of raw materials, reduction in productivity, etc., and a molding material switching method and molding material used therefor The purpose of the present invention is to provide a supply device.

[0012]

According to a first aspect of the present invention, there is provided a method according to the present invention, wherein when a molding material is switched in extrusion molding, a former molding material is supplied to the former molding material while the latter is supplied. Are mixed and supplied, then the supply of the former molding material is stopped, and only the latter molding material is supplied, thereby switching to the later molding material.

According to a second aspect of the present invention, there is provided an apparatus for supplying a molding material, comprising: a main hopper provided on an extruder; a plurality of sub-hoppers accommodating the molding material; and a molding material in each sub-hopper. A separate discharge means for discharging into the hopper, a stirring and mixing means for stirring and mixing the molding material discharged from the sub hopper in the main hopper, and forming the extruder below the stirring and mixing means. It is characterized by having material supply means.

According to a third aspect of the present invention, there is provided an apparatus for supplying a molding material according to the present invention, comprising inputting operating conditions of a molding material supplying means to an extruder, a barrel inner volume of an extruder, and an inner volume of an extrusion die. Is configured to calculate the time required for the extruded raw material to reach the tip of the extrusion molding die, and to control the operation of the discharge means of the sub hopper based on the calculation result.

According to a fourth aspect of the present invention, there is provided an apparatus for supplying a molding material according to the present invention, wherein a color difference detecting means for detecting a change in the color tone of a parison discharged from the mold is provided at the tip of the extrusion molding die. The operation of the discharge means of the sub hopper is controlled based on the detection result of the means.

(Function) The method according to the first aspect of the present invention is characterized in that the method according to the first aspect of the present invention comprises the steps of: Since the switching is gradually made to the molding material, the drift or stagnation of the molten resin due to the sudden change in the fluidity, such as when the composition is rapidly changed from the preceding molding material to the later molding material, hardly occurs. In addition, since the temperature conditions of the extruder and the mold are easily adjusted from the conditions suitable for the former molding material to the conditions suitable for the later molding material during the switching of the molding material, thermal decomposition can be avoided.

According to a second aspect of the present invention, the molding material supply device discharges the molding material individually from the plurality of sub-hoppers into the main hopper and agitates and mixes them by the agitating and mixing means in the main hopper. Since the material can be homogenized and supplied to the extruder, the composition can be changed more accurately, uniformly, and gradually as compared with the case where the former molding material and the latter molding material are manually mixed. Also, manual work is reduced.

According to a third aspect of the present invention, there is provided an apparatus for supplying a molding material to an extruder, which includes operating conditions (a charge amount, a rotation speed, a supply amount, etc.) of a molding material supply means, an inner volume of a barrel and a mold of the extruder. By inputting, the time until the extruded material reaches the tip of the extrusion mold is calculated, and after the discharge of the previous molding material to the main hopper is stopped,
Appropriate timing of the operation for switching to the mixed molding material of the former molding material and the latter molding material is calculated, and the switching operation is automatically performed. Therefore, a switching operation error is unlikely to occur, and almost no manual operation is required.

Further, according to a fourth aspect of the present invention, there is provided the apparatus for supplying a molding material according to the present invention, wherein the color difference at the time of switching from the former molding material to the mixed molding material of the former molding material and the latter molding material, The color difference at the time of switching to the molding material can be detected, and based on those results, the discharge means of the sub hopper is operated at the appropriate timing to the previous molding material, mixed molding material, and later molding material, The switching operation of the molding material is automatically performed. Therefore, a switching operation error is unlikely to occur, and almost no manual operation is required.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory view showing an example of the supply device of the molding material of the present invention. The main hopper 2 is installed on the extruder 1, and two sub hoppers 31 and 32 having smaller contents than the main hopper 2 are installed on the main hopper 2. Molding materials having different compositions are stored. Sub hoppers 31, 32
The chute portions 311 and 321 at the lower end of the are opened in the main hopper 2, and the chute portions 311 and 321 are provided with a shutter 4. Below the shutter 4, a rotary valve capable of adjusting the number of rotations to several stages is provided. 51 and 52 are provided.

Chutes 311 and 32 in main hopper 2
Below 1 is a stirrer 6 having two ribbon-shaped stirring blades.
Are provided, and the two stirring blades having the same helix angle in the same direction are rotated in the opposite direction by the gear 7, so that the powdery molding material in the main hopper 2 is uniformly moved while moving in the left-right direction. Is stirred. The rotation speed of the stirring blade is 20-100
Continuously variable speed is possible in the range of rpm. 8 is the main hopper 2
This is a screw feeder for supplying the molding material in the extruder 1. Reference numerals 91 and 92 denote level detectors of the molding material in the main hopper 2, and 10 denotes a mold.

Next, the operation and operation when the molding material is switched from the B composition to the A composition in Table 1 by the molding material supply apparatus shown in FIG. 1 will be described. Sub hopper 31
And the sub-hopper 32 stores a molding material having a B composition. Up to now C-PV with B blend
Since the extrusion of the C tube has been performed, the B compound in the sub hopper 32 is discharged into the main hopper 2 by the rotary valve 52, and the main hopper 2 is filled with the molding material of the B compound.

First, the rotary valve 52 is stopped, and B
The discharge of the compound from the sub hopper 32 to the main hopper 2 is stopped. The screw feeder 8 is kept rotating at the same number of revolutions to consume the B compound remaining in the main hopper 2. Then, when the molding material in the main hopper 2 is almost exhausted and the lower level detector 92 indicates that the main hopper 2 is full, the rotary valves 51 and 52 are simultaneously started, and the A and B compositions are almost equal. Main hopper 2 each
Discharge inside. At the same time, the stirrer 6 is started. As a result, the compound A discharged from the sub hopper 31 into the main hopper 2 and the compound B discharged from the sub hopper 32 into the main hopper 2 are uniformly mixed.

The molding material thus uniformly mixed in the main hopper 2 is extruded by the screw feeder 8 into the extruder 1.
Supplied to Then, when it is visually confirmed that the molten resin in the mixed portion of the B compound and the A compound has begun to be discharged from the mold 10, the rotary valve 52 is stopped, and only the rotary valve 51 is operated. Only the A compound is supplied to the extruder 1.

As described above, by using the molding material supply device shown in FIG. 1 and switching from B blending to A blending by the above-described operation, the switching from B blending to A blending is not abrupt. Is gradually performed through the mixing and blending of B and B (tentatively referred to as C blending), so that the fluidity of the molten resin changes suddenly in the mold and drift occurs, or as a result of the drift, the B blend remains in the mold for a long time. To avoid thermal decomposition. This eliminates the need for special preparation of a stop raw material for switching from B blend to A blend. Further, the labor for switching is greatly reduced, and the work becomes easy.

FIG. 2 is an explanatory view showing another example of the molding material supply apparatus of the present invention. In FIG. 2, reference numeral 11 denotes an arithmetic unit of the extruder control system, and reference numeral 12 denotes a control unit. The arithmetic unit 11 stores the barrel content V1, the mold content V2, the rotational speed r of the screw feeder 8 detected by a rotational speed sensor (not shown),
The detection values and the like of the level detectors 91 and 92 can be input, and from these numerical values, the time until the molding material is discharged from the tip of the mold 10, that is, the time that passes through the extruder 1 and the mold 10. t = (V1 + V2) / q (q is a supply amount corresponding to the rotation speed r of the screw feeder 8, that is, the extruder 1
Has the function of calculating the amount of extrusion. That is, the function of stopping the operating rotary valve, stopping the discharge of the molding material in the sub hopper to the main hopper, and calculating the timing of the subsequent switching operation of the molding material, whereby the rotary valve 51, It has a function of calculating timings such as start / stop of the 52.

Next, the operation and operation when the molding material is switched from the B composition to the A composition in Table 1 by the molding material supply apparatus shown in FIG. 2 will be described. The barrel content V1 of the extruder 1 and the content V2 of the mold 10 are manually input to the arithmetic unit 11, and the rotation speed r of the screw feeder 8 is input. In addition, the detection values of the level detectors 91 and 92 (that is, the remaining amount of the compound B in the main hopper 2) are also input, and a command to stop the rotary valve 52 is issued to the arithmetic unit 11.

Based on the input data, the arithmetic unit 11 determines the time t until the molding material is discharged from the tip of the mold 10 and the timing at which the mixture B in the main hopper 2 is cut off (that is, the main hopper 2 is empty). ), The start timing of the rotary valves 51 and 52, the final stop timing of the rotary valve 52, and the like, and outputs the result to the control unit 12 as a control signal. The controller 12 receives the control signal output from the calculator 11 and controls the operation of the rotary valves 51 and 52 according to the calculated result. Further, the stirrer 6 is driven while both the rotary valves 51 and 52 are being driven, whereby the A compound discharged from the sub hopper 31 into the main hopper 2 and the A mixture discharged from the sub hopper 32 into the main hopper 2 are discharged. The blended B is uniformly mixed.

The molding material uniformly mixed in the main hopper 2 is supplied to the extruder 1 by a screw feeder 8. After that, the control unit 1 according to the calculation result of the calculation unit 11
2 emits a control signal, and the control signals operate the rotary valves 51 and 52 and the stirrer 6, and finally only the A compound is supplied to the extruder 1 via the C compound to switch from the B compound to the A compound. Ends.

As a result, the switching from the B-combination to the A-composition is automatically and smoothly performed without running out of raw materials and without excessively long switching time.
The resin does not drift, stay, or thermally decompose in the mold 10. Further, the occurrence of mistakes due to manual work can be avoided, and the labor for switching can be greatly reduced, thus facilitating the work.

FIG. 3 is an explanatory diagram showing still another example of the molding material supply apparatus of the present invention. Reference numeral 13 denotes a color measurement unit (sensor) of a non-contact type color difference detection unit provided at the tip of the mold 10.
Thus, the color tone of the surface of the parison P discharged from the mold 10 can be identified with high accuracy and high speed. Reference numeral 14 denotes a comparison operation unit, which can recognize as a color difference when a difference between the color tone detected by the colorimetric unit 13 and a preset color tone exceeds a certain value. The comparison operation unit 14 includes a rotation speed r of the screw feeder 8 (accordingly, the supply amount q), a level detector 91,
The detection values of 92 are inputted, and the rotary valves 51 and 52 are provided in the same manner as the arithmetic unit 11 of the molding material supply device shown in FIG.
And a function of outputting a control signal to the control unit 15.

Next, the operation and operation when the molding material is switched from the B composition to the A composition in Table 1 by the molding material supply apparatus shown in FIG. 3 will be described. In accordance with the above operation, from B blend to B blend and A blend blend (C blend)
When the colorimetric unit 13 detects that the parison P discharged from the tip of the mold 10 has changed from B blend to C blend, the comparison operation unit 14 compares and calculates the color difference.
The rotary valve 52 is stopped, and the rotary valve 51 is stopped.
, And finally only the A compound is supplied to the extruder 1.

In this way, without causing a shortage of the raw material and without making the switching time too long,
Since the switching from the blending to the A blending through the C blending is performed automatically and smoothly, the resin drifts, stays,
Alternatively, there is no thermal decomposition. In addition, the occurrence of mistakes due to manual work is reduced, and the labor for switching is reduced.

The embodiments of the present invention have been described above, but the present invention also includes design changes and operation procedure changes without departing from the gist of the present invention. For example, in the above embodiment, the case of the C-PVC pipe has been described.
It may be an extruded product of a PVC tube or other products or a product other than a tube. Further, in the above-described embodiment, the case of switching from the B composition to the A composition shown in Table 1 has been described. However, the case of switching from the A composition to the B composition is almost the same, and is included in the present invention.

In the above embodiment, the means for discharging from the sub hopper is a rotary valve, but may be a screw feeder, a vibration feeder or the like. Also,
The secondary hopper may be a hopper loader with a pneumatic conveyor and may be installed on the floor instead of on the primary popper.

[0036]

As is apparent from the above description, the method according to the first aspect of the present invention can be applied to a method in which a molding material having a property intermediate between the former molding material and the latter molding material is used. Since the switching is gradually made to the subsequent molding material, troubles such as drifting, stagnation, and thermal decomposition of the molten resin due to a sudden change in fluidity are less likely to occur, and there is little loss of raw material and reduction in productivity due to the switching. . Further, this eliminates the need to prepare a stop raw material in which the amounts of the stabilizer and the lubricant are increased as in the related art, and can save raw material costs and man-hour costs.

In the apparatus for supplying a molding material according to the present invention, the former molding material and the latter molding material are uniformly mixed and the composition can be gradually changed. Troubles such as resin drift, stagnation, and thermal decomposition are less likely to occur. Also, manual work is reduced.

According to the third aspect of the present invention, the apparatus for supplying a molding material according to the present invention is operated so that the subsequent switching operation is performed at an appropriate timing after the discharge of the preceding molding material to the main hopper is stopped. Therefore, it is possible to switch the molding material without running out of the raw material and without generating a large amount of raw material loss. Also, since most operations are performed automatically and almost no manual work is required,
Work is easy, and there is almost no generation of dust.
Safe and sanitary.

According to a fourth aspect of the present invention, there is provided an apparatus for supplying a molding material according to the present invention, wherein the switching operation after switching from the former molding material to the mixed molding material of the former molding material and the latter molding material is performed with the former molding material. It is performed by detecting the color difference between the former molding material and the latter molding material, so it is performed after the molding material is switched reliably, preventing problems such as drift, stagnation, and thermal decomposition due to poor timing. Is done.
Further, since there is no need to visually check the color difference and the number of manual operations is reduced, the operation of switching the molding material is facilitated, and the occurrence of operation errors is reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an example of a molding material supply device of the present invention.

FIG. 2 is an explanatory view showing another example of the molding material supply device of the present invention.

FIG. 3 is an explanatory view showing still another example of the molding material supply device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Extruder 2 Main hopper 31, 32 Sub hopper 51, 52 Rotary valve 6 Stirrer 8 Screw feeder 91, 92 Level detector 10 Die 11 Operation part 12, 15 Control part 13 Color measurement part (sensor) 14 Comparison operation part P Parison

Claims (4)

[Claims] When a molding material is switched in extrusion molding, a preceding molding material is supplied and mixed with a later molding material, and then the supply of the former molding material is stopped. A method of switching a molding material in extrusion molding, characterized in that the molding material is switched to a later molding material by supplying only the material. 2. A main hopper provided on the extruder,
It has a plurality of sub-hoppers for accommodating the molding material and individual discharge means for discharging the molding material in each sub-hopper into the main hopper, and the main hopper has the stirring of the molding material discharged from the sub-hopper. A molding material supply device, comprising: a stirring and mixing means for mixing; and a molding material supply means to the extruder below the stirring and mixing means. 3. An operating condition of the molding material supply means to the extruder, an inner volume of the extruder barrel, and an inner volume of the extruding die are inputted, and the extruded raw material reaches the tip of the extruding die. 3. The molding material supply apparatus according to claim 2, wherein a time is calculated, and the operation of the discharge means of the sub hopper is controlled based on the calculation result. 4. A color difference detecting means for detecting a change in the color tone of the parison discharged from the mold at the tip of the extrusion mold, and operating the discharge means of the sub hopper based on the detection result of the color difference detecting means. 3. The molding material supply apparatus according to claim 2, wherein the apparatus is configured to control the pressure.