JPS6014687B2 - Extrusion method for additive-containing polymers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to extrusion processes for additive-loaded polymers, and in particular to improvements in additive switching techniques.

In recent years, with the diversification of market demand for plastic extrusion molded products, production sites have been forced to produce a wide variety of products in small quantities, and as a result, it has become necessary to constantly change additives.

On the other hand, in recent years, polymer extrusion equipment has generally been made larger, faster, and larger in capacity.

In such equipment, a decrease in the operating rate due to suspension of operation is the worst thing to do, so it is desirable that the above-mentioned additive changeover be performed quickly and easily. Furthermore, from the viewpoint of quality control, since air bubbles and modified polymers (generated due to abnormal liquid accumulation in the pipe) are likely to occur during switching, it is strongly required to prevent such occurrences. This invention is an attempt to meet these demands, and its gist is to branch the main line of the base polymer into two sub-lines for injecting different additives, and to prevent the predation in one of the sub-lines. After the completion of the process, the introduction of the base polymer in the other sub-line is stopped, and the base polymer and additives are mixed in a static mixer.

A more detailed explanation will be given below with reference to the accompanying drawings. In each figure, elements having substantially the same structure and function are designated by the same reference numerals. FIG. 1 shows an example of an apparatus for carrying out the present invention, in which the die of the discharge port is used as a lead port.

A main line 4 from the base polymer extruder 3 branches into two sub-lines 1 and 2. In the first subline 1,
An inlet valve 11, an inlet 13 for additive A with valve 12, a static mixer 14 and a die 15 are arranged. Similarly, the second sub-line 2 is also provided with an inlet valve 21, an inlet 23 for additive B equipped with a valve 22, a static mixer 24, and a die 25, respectively. Switching from additive A to additive B occurs in the following order.

First, the introduction valve 11 is open and the introduction valve 21 is closed, then the introduction valve 21 is opened, and then the additive B injection valve 2 is started.
Open 2. In this case, it is better not to open it all at once. As a result, the base polymer flows to the second sub-line, additive B is injected, and both are mixed in one mixer 24, and this mixture is pre-fed from the die 25.

Next, the introduction valve 21 and the additive injection valve 22 are fully opened, and then the introduction valve 11 and the additive B injection valve 12 on the first sub-line side are closed.

Thereafter, the base polymer mixed with additive B is successively discharged from the die 25. Note that in each sub-line 1/2, the downstream side of the introduction valve 11/21 can be removed, so in the above example, after the first sub-line 2 is fully activated, it is in the inactive state. The downstream side of the introduction valve 11 of the first sub-line may be removed and cleaned.

In the apparatus shown in FIG. 2, a common static mixer 5, a die 6, and a separate bleed port are used for both lines 1.2.

The first sub-line 1 for the additive A is provided with an inlet valve 11, an additive inlet 13, a feed inlet 16 and a delivery valve 17, and the part between the valves 11 and 17 is removable. It is configured. The second sub-line 2 for additive B also has an inlet valve 21, an additive inlet 23, and a bleed port 2.
6 and a delivery valve 27 are provided, and the portion between both valves 21 and 27 is configured to be removable. When switching from additive A to additive B, first open the introduction valve 21 of the second sub-line 2, perform sufficient bleed with the delivery portion 27 closed (while keeping it closed), and then open the delivery valve 27.

Incidentally, it is more convenient if the mixer 5 and the die 6 can also be removed and replaced at the time of this changeover.

The apparatus shown in FIG. 3 attempts to switch additives while maintaining high precision in the flow rate discharged from the die.

The first subline 1 for additive A is provided with an inlet valve 11, a base polymer metering pump 191, a static mixer 14, and a die 15, and the additive A in the tank 18 is It is supplied to the subline 1 downstream of the pump 191 via a metering pump 192 .

The second subline 2 for the additive 8 is provided with an inlet valve 21, a base polymer cumulative metering pump 291, a static mixer 24, and a die 25, and the additive B in the tank 28 is provided with an additive metering pump 291, a static mixer 24, and a die 25. V is supplied to the sub line 2 via the pump 292 on the downstream side of the pump 291 .

The main line 4 is provided with a pressure detector 7, which controls the pressure (screw rotation speed) of the extruder 3. For example, when switching from additive A to additive B,
The discharge bases of the metering pumps 191, 192 of the first subsidiary line are left as they are, and the metering pumps 291, 29 of the second subsidiary line 2 are
Start 2.

Then, the introduction valve 21 is opened. After sufficient bleeding, the metering pumps 191, 192 of the first sub-line are stopped, and then the introduction valve 11 thereof is closed. In this example, switching to sub line 2 is performed while discharging from sub line 1, so the switching time can be made shorter than in the example shown in FIG. In the example shown in FIG. 4, a three-way valve 8 is used at the branch point from the main line 4 to the sub lines 1 and 2.

Figure 5A shows the state of the valve 8 during normal discharge, and Figure 5B
The state of the valve 8 during bleed is shown in FIG. According to this invention, the main line for the base polymer is branched into two sub-lines, and different additives are injected in each line.
Since the additive is changed depending on which sub-line is selected, there is little loss of labor and time, and it is possible to start discharging without generating bubbles or modified polymer.

[Brief explanation of the drawing]

FIGS. 1-4: Block diagrams showing various examples of apparatus for carrying out the invention. FIGS. 5A and 5B are explanatory diagrams showing the operation of the three-way valve used in the device shown in FIG. 4. 1, 2...Sub-inlet, 4...Base polymer main line, 3...Base polymer extruder, 11, 21...Introduction valve, 13, 23...
Additive inlet, 14, 24, 5... Static mixer, 15, 25, 6... Die, 16, 26... Bleed port, 17, 27... Delivery valve, 18, 28... ...Additive tank, 191,192,291,292...Measuring pump, 7...Pressure detector, 8...Three-way valve. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 A Figure 5 B

Claims (1)

[Scope of Claims] 1. Two sub-lines branching from the main line 4 for the base polymer and comprising inlet valves 11/21 and injection ports 13/23 for different additives A/B and bleed ports in this order. 1 and 2, and when switching from additive A injected in the first sub-line 1 to additive B injected in the second sub-line 2, a part of the base polymer in the main line is first transferred to the second sub-line 2. The base polymer is introduced into the sub line 2, and after a part of the introduced base polymer is combined with the second additive B, it is all extracted from the bleed port, and when the bleed is completed, the base polymer is introduced into the first sub line 1. The introduction of the polymer is stopped and the base polymer and additives A/B are mixed in a static mixer. An extrusion method for additive-containing polymers comprising: