JPS61266222A - Extrusion molding and device therefor - Google Patents

Abstract

PURPOSE:To permit omission of drying process as well as inexpensive and stable extrusion by a method wherein material is dried and plasticized in the plasticizing machine of first stage and is mixed and pressurized in the extruding machine of second stage to extrude it. CONSTITUTION:The material resin, introduced into the two-shaft vent plasticizing machine 1 from a hopper 8, is plasticized until arriving at the first vent port 11 under being heated to a temperature up to 20 deg.C higher than the temperature of melting point or softening point of the resin and moisture or volatile material is extracted from the vent port 11 by a vacuum pump 14, thereafter, is heated further and undergoes compression and kneading. Subsequently, the resin material is deaerated sufficiently in the section of the vent port 12 under a pressure higher than 150Torr and, thereafter, is kneaded further. Then, the material resin is introduced into the melt extruding machine 15 through an extruding port 9 and a connecting pipe 10 and undergoes sufficient pressurizing and kneading, thereafter, is extruded by a gear pump 23 through a filter 24 under receiving the control of the extruding speed thereof.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an extrusion molding method and an apparatus therefor, and in particular to a method and method suitable for extrusion molding of a hygroscopic resin or a resin containing volatile substances. It is related to the device.

[Prior Art] As a method of melting and extruding a resin containing water such as polyester or polyamide, or a thermoplastic resin containing a low molecular weight volatile substance (hereinafter these resins may be abbreviated as moist resin), The method used is to dry the raw material with a dryer, then introduce it into an extruder and extrude it. As the dryer, a paddle dryer, a hopper dryer, a fluidized drying oven, etc. are usually used.

However, in the extrusion method using these dryers, the amount of heat consumed in the dryer is large and is not economical.

On the other hand, JP-A-57-15946 describes a method of extruding polyester without drying it using a vent type extruder. Further, JP-A-57-9:3118 describes that sheets and films can be extruded using a vent type extruder when the moisture content of the raw materials is not very high.

[Problems to be Solved by the Invention] However, as a result of various studies conducted by the present inventors regarding the extrusion of moist resin, the following problems exist in the extrusion method using a vented extruder. I found this.

That is, when a vented extruder is used, it is possible to extrude a moist resin, but the extrusion conditions and the physical properties of the resulting product are not necessarily good.

In other words, when extruding a moist resin using a vented extruder, although the intrinsic viscosity of the resin is at least a satisfactory value, the uniformity and other physical properties of the molded product cannot be obtained using a normal extruder. It becomes inferior to molded products. L/
It is presumed that if a vented extruder with a D = 50 or so is used, a certain degree of uniform mixing will be possible and the resulting molded product will be highly uniform, but such an extruder with a large L/D The amount of work involved is extremely large, requiring an extremely large-capacity electric motor, which is impractical. Note that L is the effective length of the extrusion screw, and D is its diameter.

In normal cases, the standard L/D is about 20 to 27.

In addition, according to the results of the studies conducted by the present inventors, it was found that a twin-screw vent extruder can perform more stable extrusion than a single-screw vent extruder. If it is, the temperature distribution of the molten product will be poor, and
Discharge pressure fluctuations are also large, and it is difficult to increase the pressure at the tip of the extruder.

[Means for solving the problem] In the present invention, a vent type plasticizer and an extruder are installed in series, the first stage plasticizer dries and plasticizes the raw material, and the second stage plasticizer dries and plasticizes the raw material.
The extruder in the second stage mixes and pressurizes the raw materials sent from the plasticizer to perform extrusion, and is designed to extrude moist resin without going through a drying process. This is what I did.

The present invention will be explained in more detail below.

In the present invention, target resins include resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene-26-naphthalate, polycarbonate, and polyamide, copolymers containing these resins as main constituent units, blends thereof, etc. can be mentioned. Furthermore, resins containing additives such as modifiers and stabilizers are also included. Accordingly, the method of the present invention makes it possible to obtain a good extrusion molded material even if these resins contain water or volatile substances.

In the present invention, raw materials such as thermoplastic resin raw materials such as flakes or chips are first introduced into a plasticizing machine, and the raw material resin is dried and plasticized.

A vent type plasticizer is used as the plasticizer. The vent-type plasticizer may be either a single-shaft vent plasticizer or a twin-shaft vent plasticizer.

A twin-screw vent plasticizer can perform more stable extrusion molding.

The vent type plasticizing machine preferably has at least two vent ports, a first vent port on the upstream side of the resin flow and a second vent port on the downstream side. By using such a plasticizing machine with multiple vent ports, it is possible to achieve the same intrinsic viscosity and other physical properties as the extrudate obtained by drying the raw material with a -H dryer and then introducing it into the extruder as in the past. Extrudates can be obtained with

That is, when using a plasticizing machine with multiple vent ports, the resin that has passed through the upstream vent port is heated, compressed, and mixed again, and then degassed again in the downstream vent hole. can.

By performing this degassing process multiple times, it is possible to reliably reduce the moisture or other volatile substances contained in the raw resin to a practically acceptable level.

Furthermore, by setting the temperature t of the resin at the vent port on the upstream side of the resin flow to be equal to or higher than the boiling point or sublimation point of water or volatile substances contained in the resin, reliable degassing can be performed. In addition, this temperature E is set to T+20°C or lower, more preferably T+5°C or lower, particularly preferably T'C or lower, where T is the melting point or softening point of the resin, thereby further suppressing the decomposition of the resin. It is possible to reliably prevent this.

In addition, the resin is degassed (drying) using a vent-type plasticizing machine.
When plasticizing is carried out, the pressure at the vent port is 150 Torr or less, preferably 70 Torr or less, particularly preferably 2 Torr or less.
By setting the pressure to 0 torr or less, hydrolysis of the resin can be suppressed.

The raw material resin that has been dried (deaerated) and plasticized by the plasticizer is then supplied to the extruder, where it is mixed, pressurized, and extruded.

Next, preferred embodiments of the extrusion molding apparatus of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional configuration diagram showing an example of an extrusion molding apparatus of the present invention. In FIG. 1, l is a two-shaft vent plasticizing machine, in which a screw 3.4 is installed in the cylinder 2,
It is rotationally driven by the power of an electric motor 6 transmitted via a reduction gear 5.

A hopper 8 is provided at the raw material introduction lower part of the cylinder 2, while an extrusion port 9 is connected to a melt extruder 15, which will be described later, via a connecting pipe IO.

The cylinder 2 is provided with two vents, a first vent 11 on the resin flow side and a second vent 12 downstream from it, each connected to a vacuum pump 14 via piping 13, and connected to the cylinder 2. It is possible to remove air from within the 2.

The melt extruder 15 has a cylinder 16, a screw 17 installed in the cylinder 16, an electric motor 18 for driving the screw 17, and a speed reducer 19. The raw material introduction port 20 of this cylinder 16 is connected to the extrusion port 9 of the twin-screw vent plasticizer 1 through the connecting pipe 10. The connecting tube 10 is equipped with a heat retaining means 10a such as a heater for keeping the resin inside the connecting tube warm. Further, a pressure sensor 21 for detecting the pressure inside the connecting pipe 10 is installed in the connecting pipe 10, and the rotation of the electric motor 6 is suppressed so that the pressure inside the connecting pipe 10 becomes a constant value.

A gear pump 23 is connected to the extrusion port 22 of the cylinder 16, and a filter 24 is connected to the downstream side of the gear pump 23. A pressure detection sensor 25 is connected to the outlet side of the filter 24.
is provided. The electric motor 18 is controlled to change the rotational speed of the screw 17 based on the detected value of the sensor 25 so that the pressure downstream of the filter 24 is constant.

In the extrusion molding apparatus configured in this way.

2-shaft vent plasticizing machine from hopper 8! The resin as a raw material introduced into the chamber is heated and plasticized to some extent before reaching the first vent 11, and water or volatile substances are extracted from the first vent 11 by a vacuum pump 14. Further, the resin passing through the first vent 11 is further heated, compressed and kneaded, and then sufficiently degassed in the $2 vent 12. 2nd ventro 1
The raw material that has passed through section 2 is further kneaded and introduced into the melt extruder 15 via the extrusion port 9 and the connecting pipe IO.

After being sufficiently pressurized and kneaded in the melt extruder 15, it is extruded through a filter 24 while the extrusion speed is adjusted by a gear pump 23.

In addition, like the extrusion device shown in Fig. 1, a twin-screw vent plasticizing machine is used.
If the connecting pipe 10 between the and melt extruder 15 is provided with a heat retaining means 10a, the inside of this connecting pipe 10 may be filled with the raw material extruded from the twin-screw vent plasticizer 1, or may be filled to some extent with the raw material extruded from the twin-screw vent plasticizer 1. A void may be provided, and this void may be filled with an inert gas such as nitrogen gas.

FIG. 2 is a configuration diagram showing the main parts of an extrusion molding apparatus according to a different embodiment.

In the embodiment shown in FIG. 2, a box 26 is installed in the middle of the connecting pipe IO, and a resin 27 is temporarily stored in the box 26.

A gap 28 is formed in the upper part of the box 26, and nitrogen gas for sealing can be introduced into the gap 28 from a pipe 29. Furthermore, the box 26 is equipped with sensors 30 and 31 that detect the level of the resin 27, and the output values of the sensors 30 and 31 are controlled by the control means of the electric motor 6 for driving the two-shaft vent plasticizing Jal (see FIG. 1). is input.

That is.

In the embodiment shown in FIG. 2, the screw rotation speed of the two-screw vent plasticizer 1 is adjusted so that the amount of resin 27 stored in the box 26 is at a predetermined level. 32 is a pressure sensor for keeping the pressure of N2 gas constant.

The other parts in FIG. 2 are the same as the apparatus in FIG. 1, so the same members will be described with the same reference numerals.

[Effect 1] In the present invention, since the plasticizer and the extruder are provided in two stages, fluctuations in discharge pressure are significantly reduced compared to conventional extruders. Moreover, when extrusion molding was conventionally carried out using only a vented extruder, it was necessary to set the tip pressure to a high pressure of 60 to 80 kg/c rn" due to filters, etc., whereas in the present invention, It is now possible to lower the tip pressure of a vent plasticizer to about 5 to 20 kg/ctn', and by controlling the pressure in this point, the vent plasticizer, which is the biggest weakness of the vent plasticizer, can be reduced. Problems such as up (resin flowing out from the vent port) and surging (pressure fluctuations caused by a shift in the mass balance inside the machine) have been almost completely resolved.

In addition, in the present invention, extrusion molding using an extruder installed at a later stage is extremely stable and quantitative.

Its quantitative performance is comparable to that of a gear pump.

In conventional one-stage extrusion molding, when a gear pump is installed at the tip of the extruder, satisfactory results can be obtained in terms of quantitative performance, pressure increase, etc., but there are many problems in terms of kneading the raw resin, especially when the resin When trying to increase the discharge rate without raising the temperature, a gear pump cannot handle the process. The extruder allows mixing, pressurization and stable extrusion to be carried out simultaneously, which is very advantageous.

[Examples] The present invention will be specifically explained below with reference to examples and reference examples, but the present invention is not limited to the following examples unless it exceeds the gist of the invention.6 For convenience, reference examples will be given first. List.

Reference Example 1 A polyethylene terephthalate resin having an intrinsic viscosity of Iv=0.60 was dried in a hopper dryer at 180° C. for 3 hours to have a water content of 15 ppm. Using this resin as raw material,
When extruded using an extruder (φ200) with L/D = 30 at a back pressure (discharge pressure) of 130 kg/crn', the pressure fluctuation was ±2 kg/cm'', and the resin temperature was 289 to 291''O. Met.

The intrinsic viscosity of the obtained sheet was Iv=0.59, and an extremely good sheet could be obtained (production volume 800k).
g/hr).

Reference example 2 A polyethylene terephthalate resin with an intrinsic viscosity Iv=0.59 and a water content of 0.2% is used as a raw material, and this raw material is L/D
= Back pressure 90 k with 30 1-vent extruder (φ40)
When extruding at g/c rn', the pressure fluctuation was ±4 kg/c, and the resin temperature was 291~3
It was 00℃. The intrinsic viscosity of the obtained sheet is I v=
0.54, and it was not possible to obtain a high-quality sheet (production amount: 18 kg/hr).

From the results of Reference Examples 1 and 2, when the moisture content of the raw material is low, a good sheet can be obtained by ordinary extrusion molding, but when the moisture content of the raw material is high, a vented extruder can be used. It is clear that it is not possible to obtain a good sheet with this method.

Reference Example 3 The same raw materials as Reference Example 2 were used in a twin-screw, two-vent extruder (φ65) with L/D=30 at a back pressure of 40 kg/c rn.
When I pushed it out, the pressure fluctuation was ±8 kg/c
tn', and the resin temperature was 288-292°C.

The intrinsic viscosity of the obtained sheet was Iv = 0.58, and although there were no physical problems, the thickness of the sheet varied significantly, and the obtained sheet obtained a high-quality film with a uniform thickness. I couldn't.

Note that the sheet production rate was 120 kg/hr.

From this result, a twin-screw, two-vent extruder can produce a sheet with a quality that is reasonably satisfactory in terms of intrinsic viscosity, but the thickness of this sheet is uneven, resulting in a high-quality film. It is clear that it is unsuitable as a manufacturing raw material.

Reference Example 4 Extrusion was carried out in the same manner as in Reference Example 3, except that a gear pump was attached to the tip of the extruder and the pressurized constant feed operation was performed. Extruder output: 120 kg/h
In r. Gear pump outlet pressure is 105 kg/
The pressure fluctuation was ±0.5 kg/crn'' and the resin temperature was 287-292°C. However, when the extruder discharge rate was increased to 200 kg/hr, the resin temperature was 290-297°C. It was difficult to extrude properly.

From this result, it is clear that the combination of a two-vent extruder and a gear pump has no problems with pressure increase and quantitative performance, but there is a problem in that increasing the discharge rate causes the resin temperature to rise.

Example 1 L/D=30 as a front-stage plasticizing machine. 2 with a diameter of 65mm
Using a two-shaft vent extruder, the second stage extruder is -rL/
D=20. Using an l-shaft extruder with a diameter of 90 mm, pellets of polyethylene terephthalate with an intrinsic viscosity Iv = 0.60 and a water content of 0.25% were processed under a back pressure of 15% in a vent extruder.
kg/Cz, extruder back pressure 120kg/crn'
I pushed it out.

At this time, the pressure fluctuation was ±1 kg/ctn', and the resin temperature was 288 to 290°C (production volume 120 kg
/hr).

The intrinsic viscosity of the obtained sheet is Iv=0.58-0.59
Therefore, it was possible to obtain an extremely good sheet.

Further, although extrusion was carried out with the production rate increased to 200 kg/hr, the resin temperature did not rise and good extrusion could be carried out.

Example 2 Example 1 was prepared using polyethylene terephthalate flakes (pulverized film) with an intrinsic viscosity of Iv=0.58 as a raw material.
The back pressure of the vent extruder was 15 kg/
cm'', extruded at a back pressure of 120 kg/crn' of the extruder.The pressure fluctuation at this time was ±l kg/cm''.
cr rr+', and the resin temperature was 289-291°C (production amount 120 kg/hr).

The intrinsic viscosity of the obtained sheet was Iv=0.58, and an extremely good sheet could be obtained.

Example! and 2, it is clear that according to the extrusion molding method and apparatus of the present invention, extremely good extrusion molding can be performed, and the physical properties of the obtained sheet are also extremely good.

[Effect 1] As detailed above, in the extrusion molding method of the present invention, a plasticizing machine and an extrusion mold are installed in two stages in series, and drying (deaeration treatment) and plasticizing of the raw material are performed in the plasticizing machine in the previous stage. The extrudate from the plasticizing machine is mixed, pressurized, and extruded in the subsequent extruder, and the hygroscopic resin powder or resin powder containing volatile substances is removed using a dryer, etc. Good extrusion molding can be performed without providing a drying means. Therefore, energy costs such as a drying heat source or drying operation are omitted, so that stable extrusion molding can be easily performed at low cost.

Moreover, the resulting extrusion molded product such as sheet or film is
It has an extremely uniform composition and film thickness, resulting in high quality and high commercial value, and also extremely high productivity.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional configuration diagram illustrating the outline of the extrusion molding apparatus of the present invention, and FIG. 2 is a partial cross-sectional configuration diagram showing another example of the connection part between the plasticizer and the extruder of the extrusion molding apparatus of the present invention. It is. ■...Twin-screw vent type plasticizer, 10...Connecting pipe, 15...Melt extruder, 3.4.17...Screw, 2.16...Cylinder, 6.18...・Electric motor, 5.19...Reducer, 21.25.32...Pressure sensor, 30.31...Level control sensor.

Claims (9)

[Claims] (1) When extrusion molding resin as a raw material, first introduce the resin into a vent type plasticizer to dry and plasticize the raw material, then introduce it into an extruder, mix, increase pressure, and extrude. An extrusion molding method characterized by: (2) The extrusion molding method according to claim 1, wherein the resin as a raw material contains water or other volatile substances. (3) A patent characterized in that when drying and plasticizing raw materials in a plasticizing machine, moisture or volatile substances are extracted to the outside of the plasticizing machine through at least two vent ports provided in the resin flow direction. An extrusion molding method according to claim 2. (4) The pressure at the vent port inside the plasticizing machine is 150
Claim 3 characterized in that it is less than or equal to
Extrusion molding method described in Section. (5) The temperature of the resin passing through the upstream vent port is
is higher than the boiling point of water or volatile substances contained in the resin,
The extrusion molding method according to claim 3 or 4, wherein the temperature t is T+20° C. or lower, where T is the melting point or softening point of the resin. (6) An extrusion molding apparatus comprising: a vent-type plasticizer for degassing and plasticizing raw resin; and an extruder into which the raw material is introduced from the plasticizer. (7) A patent characterized in that the plasticizing machine has at least two vent ports: a first vent port and a second vent port provided downstream of the resin flow from the first vent port. An extrusion molding apparatus according to claim 6. (8) A means for detecting the pressure of the resin introduced from the plasticizer into the extruder is provided, and the amount of resin flowing out from the plasticizer is controlled so that this pressure is substantially constant. An extrusion molding apparatus according to claim 6 or 7. (9) Extrusion according to claim 8, wherein means for detecting the pressure of the resin extruded from the extruder is provided, and the amount of resin extruded from the extruder is controlled so that this pressure is substantially constant. Molding equipment.