JPH0382504A - Extruder for multi-layer parison - Google Patents

Abstract

PURPOSE:To accurately control the extrusion of a multi-layer parison by selectively detecting infrared rays radiated from the inner layer that has the highest plasticizing temperature among extruded inner layers and identifying the existing conditions of the inner layers on the basis of a detected signal. CONSTITUTION:The temperature of HDPE (high-density polyethylene) shows 190 to 210 deg.C immediately after a parison 50 is extruded, while PA has a temperature of 230 to 250 deg.C, and an adhesive layer has a temperature therebetween. Infrared rays transmitted through the HDPE to come out to the external side are separated at 180 deg.C, (200 deg.C) 220 deg.C and selectively sensed by using a high-sensitive infrared ray sensor (in this case, a CCD camera 61) with an infrared ray filter 61A that permits the infrared rays alone to pass therethrough. Upon comparison of each measured output with normal patterns stored in a normal pattern storage unit 64 by means of an identifier 63 via an image processing unit 62, whether the difference i.e. DEV between the measured output thus compared and a preset value is within a predetermined range is determined. In the case of YES, an YES display unit 65 displays YES, while in the case of NO, its DEV signal is sent to an inner-layer ring parison control circuit 72. The control circuit 72 sends a correction output signal corresponding to the DEV signal to servo valves 31, 32, and a controlled hydraulic pressure is sent to each of hydraulic cylinders 19, 20 from a hydraulic source 30.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a multilayer parison extrusion molding apparatus, and more particularly to a multilayer parison extrusion molding apparatus equipped with means for determining the condition of an inner layer using infrared rays.

[Conventional technology] Conventionally, mobile hydrocarbon containers such as automobile fuel tanks have been developed from the viewpoints of improving space utility, reducing weight, improving rust resistance and impact resistance on the inside and outside surfaces, and saving labor in the production process. Plastic tanks are already beginning to be used to replace metal tanks. However, plastic tanks contain gasoline, etc. (including alternative fuels such as gasohol).

) is a problem, and in fact, in single-layer HDPE (high-density polyethylene) tanks, the amount of permeation tends to be large because HDPE itself has a high affinity for the hydrocarbons that make up gasoline.

Since the amount of gasoline permeation is strictly regulated for environmental conservation reasons, it is necessary to take measures to prevent gasoline permeation in plastic tanks.

As means for preventing gasoline permeation, processing techniques using F2 gas and SO3 gas have been established. However, since these gases are harmful to humans, this treatment technique is not commonly used.

Another method employed is to extrude and blow mold a multilayer parison to create a multilayer plastic fuel tank.

Hitherto, multilayer plastic fuel tanks have been devised with three to five layers, each of which has an outer layer of HDPE and an inner layer of barrier-forming resin such as PA (polyamide or nylon) or ethylene-vinyl acetate copolymer saponified resin. be.

Furthermore, if these expensive barrier layers are laminated over the entire surface of the product tank, the layers will become multi-layered up to the top and bottom pinch-off areas, resulting in reduced strength in those areas, high costs, and difficulty in recycling. some multi-layered (
It is also called focused multi-layering. ) is being carried out.

In this case, it is especially necessary to guarantee that all necessary parts are multi-layered.

There are two methods for this: a method (1) of controlling the extrusion amount at the source in the parison extruder, and a method (2) of non-destructively testing the entire parison or product tank.

As method (1), a method has been announced in which the torque (current) of the extruder and the pressure obtained by subtracting the resin pressure immediately before the die from the resin pressure at the tip of the extruder have been announced. (Dr, Re1n
er Hegie, ”C0EXTRUSION
BLOW MOULDINGS OF
LARGE HOLLOW ARTICLES,
"C0EX EUROPE-86°p, 368)
(IA).

However, this method is based on the premise that the torque (current) of the extruder and the extrusion rate are proportional to each other, so if the plasticizing conditions are changed by changing the extrusion resin temperature, etc. It becomes necessary to perform correction, and it is difficult to apply it under all molding conditions.

As an improved method (1), for example,
23212, a multilayer blower characterized in that a timer is used to shift the operating timing of each solenoid valve on the injection side, and a time constant generation type control device is used to control the rise characteristics of each injection cylinder. A parison head control device for a molding machine has been proposed (IB).

However, there is a problem in fully guaranteeing the laminated state of multilayer blow products by controlling the parison extruder.
0% reliability cannot be guaranteed.

Method (2) is to remove the inner layer during molding. There is a way to monitor indirectly.

For example, as an inner layer detection means during molding, the accumulator position of the inner layer (adhesive, PA) and each resin pressure are monitored with respect to the accumulator position of the outer layer material, and each is kept within a certain tolerance range ( 2A). This method allows indirect and non-destructive layer management of the parison.

Furthermore, it is also possible to cancel out the effects of disturbances such as resin clogging and fluctuations in plasticizing conditions. Also, as important as checking the inner layer during molding, there is a non-destructive inspection technology for the inner layer of a molded multilayer plastic fuel tank. Theoretically, this can be determined by detecting the difference in resin density using ultrasound (2B).

However, since the former method is an indirect detection method, there is a problem in that sufficient reliability cannot be guaranteed. Also,
The latter type of ultrasonic inspection has the disadvantage that it cannot be performed without contact, so an ultrasonic probe is placed in contact with a plastic fuel tank that has just been blow-molded and has not been sufficiently cooled through a liquid couplant (barrier layer). It has been difficult to measure the state of existence of the inner layer at manufacturing sites.

In addition, the ultrasonic test has a problem in that the inspection range is narrow at one time, and it takes too much time to inspect the entire surface.

Another example of (2) is JP-A No. 63-260417.
As stated in the publication, inner layer material (barrier layer material)
There is a method (2C) in which a detection medium such as iron powder or short glass fibers is mixed in advance, and the distribution of the inner layer material is detected from the outside using a magnetic sensor, ultrasonic sensor, etc. after forming the parison.

However, this method naturally suffers from the disadvantages of the presence of a detection medium in the parison itself or in the blow-molded product.
It left a problem.

[Problems to be Solved by the Invention] The purpose of the present invention is to measure the presence of the inner layer (barrier layer) that cannot be directly observed during the extrusion process in a non-contact and non-destructive manner, and to feed back the results to improve the quality of multilayer parisons. An object of the present invention is to provide a multilayer parison extrusion molding device that enables accurate extrusion control.

Another object of the present invention is to provide a multilayer parison extrusion molding apparatus that is equipped with a means for determining whether or not lamination has been carried out as designed over almost the entire surface of a parison or blow-molded product within a short period of time. be.

[Means for Solving the Problems] According to the present invention, in an extrusion molding apparatus for a multilayer parison in which an outermost layer and at least one inner layer having a higher plasticizing temperature than the outermost layer are laminated, plasticizing of the extruded inner layer is provided. Extrusion of a multilayer parison characterized by comprising an infrared detecting means for selectively detecting infrared rays emitted from the inner layer having the highest temperature, and a determining means for determining the presence state of the inner layer based on a detection signal of the infrared detecting means. A molding device is provided.

EXAMPLES The present invention will be explained below in detail with reference to examples.

FIG. 1 is a cross-sectional and circuit diagram showing an accumulator head 1 and a control circuit of a five-layer parison extrusion molding apparatus according to an embodiment of the present invention.

Normally, in the case of a three-layer parison, the structure is symmetrical with the first layer/second layer/third layer (=first layer) in the thickness direction when viewed from the outside or the inside.

Similarly, in the case of a 5-layer parison, 1st layer / 2nd layer / 3rd layer / 4th layer / 5th layer (= 2nd layer)
(=first layer).

However, if necessary, it is also possible to provide an asymmetrical structure in the thickness direction, for example by providing a weather-resistant resin layer on the outer surface of the tank and a solvent-resistant resin layer (barrier layer) on the inner surface. However, it is inevitable that the extruder becomes complicated. It will also be necessary to consider the resin components and adhesives that make up each layer.

However, the plasticizing temperature of the resin forming the inner layer whose existence state is to be determined must be higher than that of the other layers.

This is because, as will be described later, it is necessary to selectively detect infrared rays emitted from the inner layer of the parison from the outside immediately after extrusion. In other words, unless the plasticizing temperature is the highest, infrared energy emitted from the inner layer cannot be detected.

In this embodiment, a case of a symmetrical three-type five-layer parison will be described.

That is, since HDPE does not have a polar group, it has poor adhesion, and since it is necessary to interpose an adhesive layer between it and PA, when an adhesive layer is also added to the layers, a symmetrical three-layer five-layer structure is obtained.

That is, when viewed from the outside, as described above, the first layer/second layer/third layer/fourth layer/fifth layer (IIDPE
) (Adhesive layer) IP A) (Adhesive layer) (HD
PE). Here, there are first layer/second layer and first layer/second layer.

FIG. 2 is a cross-sectional view taken along the line nn'' in FIG. 1, and FIG. 3 is an enlarged cross-sectional view of a main part showing the resin passage around the annular nozzle.

The structure of the accumulator head 1 is roughly as follows.

In FIGS. 1, 2, and 3, HDPE, which is the material for the first and fifth layers, is supplied from an extruder 11, passes through an annular resin passage 8, passes through a resin storage chamber 2, and is extruded by a ring plunger 5. and reaches the resin passage 10. The adhesive for the second and fourth layers is supplied by an extruder 12, passes through the accumulator 4 and the adhesive resin passage 42, and is extruded by the plunger 7.
At 13, the layers are layered. PA, which is a barrier layer, is supplied from an extruder 13, passes through an accumulator 3 and a barrier resin passage 41, is extruded by a plunger 6, is supplied to a resin passage 1o, and is layered.

That is, the slit between the die 14 and the core 15 (
It has a structure in which parisons of three types and five layers are extruded through an annular nozzle (16). Here, 40 is the core, 45 is the support part, and 6
1 is an infrared sensor (COD camera).

Rather, the main part of the present invention is the detection and detection of the inner layer existence state described below.
It lies in the means of discrimination.

The temperature of HDPE immediately after parison 50 is extruded is 19
0-210°C, while PA is 230-250°C, and the adhesive layer is in between.

Therefore, the infrared rays emitted by the internal PA or adhesive layer pass through the HDPE and exit to the outside.

A high-sensitivity infrared sensor (in this case, a COD camera 61
) for separation and selective detection at 180°C, (200°C) and 220°C. The adhesive layer is difficult to measure due to its thin thickness and low output, so the measurement may be omitted. After comparing each measured output with the regular pattern stored in the regular pattern storage device 64 via the image processing unit 62 and the discriminator 63, it is determined whether the difference from the set value, DEV, is within a certain range, that is, YES. or NO. If YES, YES is displayed on the YES display 65, and NO is displayed.
In the case of O, the DEV signal is sent to the inner ring parison control circuit 72. The inner ring parison control circuit 72 outputs a correction output signal corresponding to this DEV signal to the servo pulp 31.
．． 32, and the hydraulic pressure controlled by servo pulps 31 and 32 is sent to the hydraulic cylinders 1 from the hydraulic source 30, respectively.
Sent on 9.20. As a result, the plunger 6.7 moves by the necessary stroke simultaneously with the operation of the ring plunger 5, and the thickness of the barrier layer and the adhesive layer is adjusted from O to the set amount. In addition, the outer layer (1st layer and 5th layer)
is a mechanism that is controlled independently of the inner layer, in which the resin extruded by the extruder 11 is accumulated in the resin storage chamber 2, and the mechanism is proportionally triggered by the plunger position detector 70 that detects the raised position of the ring plunger 5. There is an outer layer parison control circuit 71, and hydraulic pressure is supplied from the hydraulic source 30 to the hydraulic cylinder 18 through the path 34 via the servo pulp 33, which is controlled by a signal output from this circuit, and is pushed down by the hydraulic cylinder 18. by the ring plunger 5 and at the same time the aforementioned plunger 6
．． 7 allows the multilayer parison 50 to be extruded. Also, ring plunger 5 and plunger 6.
A trigger signal is sent from the outer ring parison control circuit to the inner ring parison control circuit in order to synchronize and pressure balance the operation of the rings.

It goes without saying that the present invention can further improve accuracy by combining with the prior art techniques (1) and (2) described above.

The IDPE (used in the present invention) is, for example, the so-called Phillips process polyethylene produced by medium-pressure polymerization, and its trade names include BASF Lebolen (registered trademark) 4261A and Showa Nijiyo Rex (registered trademark) Super 4551H.
etc. Further, as PA, which is a nylon resin, polyamide 6:0M1046 [Toshi Amiran (registered trademark)] or the like was used.

In addition, in the present invention, only self-radiated infrared rays are measured.

However, it is also possible to selectively determine the state of existence of the inner layer by providing a separate light source such as a laser beam and transmitting or reflecting light.

[Effects of the Invention] By carrying out the present invention, all of the above objectives are achieved.

In other words, it is possible to non-contact and non-destructively measure the state of each inner layer such as the barrier layer on the multilayer parison immediately after extrusion, so the results can be fed back to the extrusion equipment to guarantee the quality of all parts. I can do it.

[Brief explanation of drawings]

FIG. 1 is a sectional/circuit diagram of an embodiment of the present invention, FIG. 2 is a sectional view taken along line nn' in FIG. 1, and FIG. 3 is an enlarged sectional view of a main part showing a resin passage around an annular nozzle. 1 Accumulator head, 2
resin storage chamber, 5, 6. 7 Plunger, 8
Annular resin passage, 11, 12. 13
Resin extruder, 16 slits (annular nozzle), 18.19.20 hydraulic cylinder,
31.32.33 Servo pulp, 40
Core, 41 Barrier resin passage, 42
adhesive resin passage, 50
Parison, 61 Infrared sensor (COD camera)

Claims (1)

[Claims] (1) In an extrusion molding device for a multilayer parison formed by laminating an outermost layer and at least one inner layer having a higher plasticizing temperature than the outermost layer, infrared rays are emitted from the inner layer having the highest plasticizing temperature among the extruded inner layers. 1. An extrusion molding apparatus for a multilayer parison, comprising: an infrared detecting means for selectively detecting the inner layer; and a determining means for determining the presence state of the inner layer based on a detection signal of the infrared detecting means.